Convert.ToBoolean 方法
重要
一些信息与预发行产品相关，相应产品在发行之前可能会进行重大修改。 对于此处提供的信息，Microsoft 不作任何明示或暗示的担保。
将指定的值转换为等效的布尔值。
| ToBoolean(SByte) |
将指定的 8 位有符号整数的值转换为等效的布尔值。 |
| ToBoolean(String, IFormatProvider) |
使用指定的区域性特定格式设置信息，将逻辑值的指定字符串表示形式转换为其等效的布尔值。 |
| ToBoolean(Object, IFormatProvider) |
使用指定的区域性特定格式设置信息，将指定对象的值转换为等效的布尔值。 |
| ToBoolean(UInt64) |
将指定的 64 位无符号整数的值转换为等效的布尔值。 |
| ToBoolean(UInt32) |
将指定的 32 位无符号整数的值转换为等效的布尔值。 |
| ToBoolean(UInt16) |
将指定的 16 位无符号整数的值转换为等效的布尔值。 |
| ToBoolean(String) |
将逻辑值的指定字符串表示形式转换为其等效的布尔值。 |
| ToBoolean(Single) |
将指定的单精度浮点数的值转换为等效的布尔值。 |
| ToBoolean(Object) |
将指定对象的值转换为等效的布尔值。 |
| ToBoolean(DateTime) |
调用此方法始终引发 InvalidCastException。 |
| ToBoolean(Int32) |
将指定的 32 位有符号整数的值转换为等效的布尔值。 |
| ToBoolean(Int16) |
将指定的 16 位有符号整数的值转换为等效的布尔值。 |
| ToBoolean(Double) |
将指定的双精度浮点数的值转换为等效的布尔值。 |
| ToBoolean(Decimal) |
将指定的十进制数字的值转换为等效的布尔值。 |
| ToBoolean(Char) |
调用此方法始终引发 InvalidCastException。 |
| ToBoolean(Byte) |
将指定的 8 位无符号整数的值转换为等效的布尔值。 |
| ToBoolean(Boolean) |
返回指定的布尔值；不执行任何实际的转换。 |
| ToBoolean(Int64) |
将指定的 64 位有符号整数的值转换为等效的布尔值。 |
- Source:
- Convert.cs
- Source:
- Convert.cs
- Source:
- Convert.cs
重要
此 API 不符合 CLS。
将指定的 8 位有符号整数的值转换为等效的布尔值。
public:
static bool ToBoolean(System::SByte value);C#
[System.CLSCompliant(false)]
public static bool ToBoolean (sbyte value);[<System.CLSCompliant(false)>]
static member ToBoolean : sbyte -> boolPublic Shared Function ToBoolean (value As SByte) As Boolean参数
- value
- SByte
要转换的 8 位带符号整数。
返回
如果 true 不为零，则为 value；否则，为 false。
- 属性
示例
以下示例将值的数组 SByte 转换为 Boolean 值。
array<SByte>^ numbers = gcnew array<SByte> { SByte::MinValue, -1, 0, 10, 100, SByte::MaxValue };
bool result;
for each (SByte number in numbers)
{
result = Convert::ToBoolean(number);
Console::WriteLine("{0,-5} --> {1}", number, result);
}
// The example displays the following output:
// -128 --> True
// -1 --> True
// 0 --> False
// 10 --> True
// 100 --> True
// 127 --> True
C#
sbyte[] numbers = { SByte.MinValue, -1, 0, 10, 100, SByte.MaxValue };
bool result;
foreach (sbyte number in numbers)
{
result = Convert.ToBoolean(number);
Console.WriteLine("{0,-5} --> {1}", number, result);
}
// The example displays the following output:
// -128 --> True
// -1 --> True
// 0 --> False
// 10 --> True
// 100 --> True
// 127 --> True
let numbers =
[| SByte.MinValue; -1y; 0y
10y; 100y; SByte.MaxValue |]
for number in numbers do
let result = Convert.ToBoolean number
printfn $"{number,-5} --> {result}"
// The example displays the following output:
// -128 --> True
// -1 --> True
// 0 --> False
// 10 --> True
// 100 --> True
// 127 --> True
Dim numbers() As SByte = { SByte.MinValue, -1, 0, 10, 100, SByte.MaxValue }
Dim result As Boolean
For Each number As SByte In numbers
result = Convert.ToBoolean(number)
Console.WriteLine("{0,-5} --> {1}", number, result)
Next
' The example displays the following output:
' -128 --> True
' -1 --> True
' 0 --> False
' 10 --> True
' 100 --> True
' 127 --> True
另请参阅
适用于
.NET 9 和其他版本
| 产品 | 版本 |
|---|---|
| .NET | Core 1.0, Core 1.1, Core 2.0, Core 2.1, Core 2.2, Core 3.0, Core 3.1, 5, 6, 7, 8, 9 |
| .NET Framework | 1.1, 2.0, 3.0, 3.5, 4.0, 4.5, 4.5.1, 4.5.2, 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2, 4.8, 4.8.1 |
| .NET Standard | 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 2.0, 2.1 |
| UWP | 10.0 |
- Source:
- Convert.cs
- Source:
- Convert.cs
- Source:
- Convert.cs
使用指定的区域性特定格式设置信息，将逻辑值的指定字符串表示形式转换为其等效的布尔值。
public:
static bool ToBoolean(System::String ^ value, IFormatProvider ^ provider);C#
public static bool ToBoolean (string value, IFormatProvider provider);C#
public static bool ToBoolean (string? value, IFormatProvider? provider);static member ToBoolean : string * IFormatProvider -> boolPublic Shared Function ToBoolean (value As String, provider As IFormatProvider) As Boolean参数
- value
- String
包含 TrueString 或 FalseString 值的字符串。
- provider
- IFormatProvider
一个提供区域性特定的格式设置信息的对象。 忽略此参数。
返回
如果 true 等于 value，则为 TrueString；如果 false 等于 value 或 FalseString，则为 null。
例外
value 不等于 TrueString 或 FalseString。
注解
如果希望在转换失败时不处理异常，可以改为调用 Boolean.TryParse 方法。 它返回一个 Boolean 值，该值指示转换是成功还是失败。
另请参阅
适用于
.NET 9 和其他版本
| 产品 | 版本 |
|---|---|
| .NET | Core 1.0, Core 1.1, Core 2.0, Core 2.1, Core 2.2, Core 3.0, Core 3.1, 5, 6, 7, 8, 9 |
| .NET Framework | 1.1, 2.0, 3.0, 3.5, 4.0, 4.5, 4.5.1, 4.5.2, 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2, 4.8, 4.8.1 |
| .NET Standard | 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 2.0, 2.1 |
| UWP | 10.0 |
- Source:
- Convert.cs
- Source:
- Convert.cs
- Source:
- Convert.cs
使用指定的区域性特定格式设置信息，将指定对象的值转换为等效的布尔值。
public:
static bool ToBoolean(System::Object ^ value, IFormatProvider ^ provider);C#
public static bool ToBoolean (object value, IFormatProvider provider);C#
public static bool ToBoolean (object? value, IFormatProvider? provider);static member ToBoolean : obj * IFormatProvider -> boolPublic Shared Function ToBoolean (value As Object, provider As IFormatProvider) As Boolean参数
- value
- Object
用于实现 IConvertible 接口的对象，或为 null。
- provider
- IFormatProvider
一个提供区域性特定的格式设置信息的对象。
返回
true 或 false，它将反映通过对 ToBoolean(IFormatProvider) 的基础类型调用 value 方法而返回的值。 如果 value 为 null，则此方法返回 false。
例外
value 是一个不等于 TrueString 或 FalseString的字符串。
示例
下面的示例定义一个实现 的 IConvertible 类和一个实现 的 IFormatProvider类。 实现 IConvertible 的类的对象保存值数组 Double 。 每个类的一个对象将 ToBoolean(Object, IFormatProvider) 传递给 方法。 如果任何未丢弃的数组值不为零，则此方法返回 true 。 对象 IFormatProvider 确定如何为此计算放弃元素。
using namespace System;
using namespace System::Collections;
// Define the types of averaging available in the class
// implementing IConvertible.
public enum class AverageType : short
{
None = 0,
GeometricMean = 1,
ArithmeticMean = 2,
Median = 3
};
// Pass an instance of this class to methods that require an
// IFormatProvider. The class instance determines the type of
// average to calculate.
ref class AverageInfo: public IFormatProvider
{
protected:
AverageType AvgType;
public:
// Specify the type of averaging in the constructor.
AverageInfo( AverageType avgType )
{
this->AvgType = avgType;
}
// This method returns a reference to the containing object
// if an object of AverageInfo type is requested.
virtual Object^ GetFormat( Type^ argType )
{
if ( argType == AverageInfo::typeid)
return this;
else
return (Object^)0;
}
property AverageType TypeOfAverage
{
// Use this property to set or get the type of averaging.
AverageType get()
{
return this->AvgType;
}
void set( AverageType value )
{
this->AvgType = value;
}
}
};
// This class encapsulates an array of double values and implements
// the IConvertible interface. Most of the IConvertible methods
// return an average of the array elements in one of three types:
// arithmetic mean, geometric mean, or median.
ref class DataSet: public IConvertible
{
private:
static Object^ null = nullptr;
protected:
ArrayList^ data;
AverageInfo^ defaultProvider;
// This method unboxes a boxed double.
double UnBoxDouble( Object^ obj )
{
return *static_cast<double^>(obj);
}
public:
// Construct the object and add an initial list of values.
// Create a default format provider.
DataSet( ... array<Double>^values )
{
data = gcnew ArrayList( (Array^)values );
defaultProvider = gcnew AverageInfo( AverageType::ArithmeticMean );
}
// Add additional values with this method.
int Add( double value )
{
data->Add( value );
return data->Count;
}
property double Item[ int ]
{
// Get, set, and add values with this indexer property.
double get( int index )
{
if ( index >= 0 && index < data->Count )
return UnBoxDouble( data[ index ] );
else
throw gcnew InvalidOperationException( "[DataSet.get] Index out of range." );
}
void set( int index, double value )
{
if ( index >= 0 && index < data->Count )
data[ index ] = value;
else
if ( index == data->Count )
data->Add( value );
else
throw gcnew InvalidOperationException( "[DataSet.set] Index out of range." );
}
}
property int Count
{
// This property returns the number of elements in the object.
int get()
{
return data->Count;
}
}
protected:
// This method calculates the average of the object's elements.
double Average( AverageType avgType )
{
double SumProd;
if ( data->Count == 0 )
return 0.0;
switch ( avgType )
{
case AverageType::GeometricMean:
SumProd = 1.0;
for ( int Index = 0; Index < data->Count; Index++ )
SumProd *= UnBoxDouble( data[ Index ] );
// This calculation will not fail with negative
// elements.
return Math::Sign( SumProd ) * Math::Pow( Math::Abs( SumProd ), 1.0 / data->Count );
case AverageType::ArithmeticMean:
SumProd = 0.0;
for ( int Index = 0; Index < data->Count; Index++ )
SumProd += UnBoxDouble( data[ Index ] );
return SumProd / data->Count;
case AverageType::Median:
if ( data->Count % 2 == 0 )
return (UnBoxDouble( data[ data->Count / 2 ] ) + UnBoxDouble( data[ data->Count / 2 - 1 ] )) / 2.0;
else
return UnBoxDouble( data[ data->Count / 2 ] );
default:
return 0.0;
}
}
// Get the AverageInfo object from the caller's format provider,
// or use the local default.
AverageInfo^ GetAverageInfo( IFormatProvider^ provider )
{
AverageInfo^ avgInfo = nullptr;
if ( provider != nullptr )
avgInfo = static_cast<AverageInfo^>(provider->GetFormat( AverageInfo::typeid ));
if ( avgInfo == nullptr )
return defaultProvider;
else
return avgInfo;
}
// Calculate the average and limit the range.
double CalcNLimitAverage( double min, double max, IFormatProvider^ provider )
{
// Get the format provider and calculate the average.
AverageInfo^ avgInfo = GetAverageInfo( provider );
double avg = Average( avgInfo->TypeOfAverage );
// Limit the range, based on the minimum and maximum values
// for the type.
return avg > max ? max : avg < min ? min : avg;
}
public:
// The following elements are required by IConvertible.
// None of these conversion functions throw exceptions. When
// the data is out of range for the type, the appropriate
// MinValue or MaxValue is used.
virtual TypeCode GetTypeCode()
{
return TypeCode::Object;
}
virtual bool ToBoolean( IFormatProvider^ provider )
{
// ToBoolean is false if the dataset is empty.
if ( data->Count <= 0 )
return false;
// For median averaging, ToBoolean is true if any
// non-discarded elements are nonzero.
else
// For median averaging, ToBoolean is true if any
// non-discarded elements are nonzero.
if ( AverageType::Median == GetAverageInfo( provider )->TypeOfAverage )
{
if ( data->Count % 2 == 0 )
return (UnBoxDouble( data[ data->Count / 2 ] ) != 0.0 || UnBoxDouble( data[ data->Count / 2 - 1 ] ) != 0.0);
else
return UnBoxDouble( data[ data->Count / 2 ] ) != 0.0;
}
// For arithmetic or geometric mean averaging, ToBoolean is
// true if any element of the dataset is nonzero.
else
{
for ( int Index = 0; Index < data->Count; Index++ )
if ( UnBoxDouble( data[ Index ] ) != 0.0 )
return true;
return false;
}
}
virtual Byte ToByte( IFormatProvider^ provider )
{
return Convert::ToByte( CalcNLimitAverage( Byte::MinValue, Byte::MaxValue, provider ) );
}
virtual Char ToChar( IFormatProvider^ provider )
{
return Convert::ToChar( Convert::ToUInt16( CalcNLimitAverage( Char::MinValue, Char::MaxValue, provider ) ) );
}
// Convert to DateTime by adding the calculated average as
// seconds to the current date and time. A valid DateTime is
// always returned.
virtual DateTime ToDateTime( IFormatProvider^ provider )
{
double seconds = Average( GetAverageInfo( provider )->TypeOfAverage );
try
{
return DateTime::Now.AddSeconds( seconds );
}
catch ( ArgumentOutOfRangeException^ )
{
return seconds < 0.0 ? DateTime::MinValue : DateTime::MaxValue;
}
}
virtual Decimal ToDecimal( IFormatProvider^ provider )
{
// The Double conversion rounds Decimal.MinValue and
// Decimal.MaxValue to invalid Decimal values, so the
// following limits must be used.
return Convert::ToDecimal( CalcNLimitAverage( -79228162514264330000000000000.0, 79228162514264330000000000000.0, provider ) );
}
virtual double ToDouble( IFormatProvider^ provider )
{
return Average( GetAverageInfo( provider )->TypeOfAverage );
}
virtual short ToInt16( IFormatProvider^ provider )
{
return Convert::ToInt16( CalcNLimitAverage( Int16::MinValue, Int16::MaxValue, provider ) );
}
virtual int ToInt32( IFormatProvider^ provider )
{
return Convert::ToInt32( CalcNLimitAverage( Int32::MinValue, Int32::MaxValue, provider ) );
}
virtual __int64 ToInt64( IFormatProvider^ provider )
{
// The Double conversion rounds Int64.MinValue and
// Int64.MaxValue to invalid Int64 values, so the following
// limits must be used.
return Convert::ToInt64( CalcNLimitAverage( -9223372036854775000, 9223372036854775000, provider ) );
}
virtual signed char ToSByte( IFormatProvider^ provider )
{
return Convert::ToSByte( CalcNLimitAverage( SByte::MinValue, SByte::MaxValue, provider ) );
}
virtual float ToSingle( IFormatProvider^ provider )
{
return Convert::ToSingle( CalcNLimitAverage( Single::MinValue, Single::MaxValue, provider ) );
}
virtual UInt16 ToUInt16( IFormatProvider^ provider )
{
return Convert::ToUInt16( CalcNLimitAverage( UInt16::MinValue, UInt16::MaxValue, provider ) );
}
virtual UInt32 ToUInt32( IFormatProvider^ provider )
{
return Convert::ToUInt32( CalcNLimitAverage( UInt32::MinValue, UInt32::MaxValue, provider ) );
}
virtual UInt64 ToUInt64( IFormatProvider^ provider )
{
// The Double conversion rounds UInt64.MaxValue to an invalid
// UInt64 value, so the following limit must be used.
return Convert::ToUInt64( CalcNLimitAverage( 0, 18446744073709550000.0, provider ) );
}
virtual Object^ ToType( Type^ conversionType, IFormatProvider^ provider )
{
return Convert::ChangeType( Average( GetAverageInfo( provider )->TypeOfAverage ), conversionType );
}
virtual String^ ToString( IFormatProvider^ provider )
{
AverageType avgType = GetAverageInfo( provider )->TypeOfAverage;
return String::Format( "( {0}: {1:G10} )", avgType, Average( avgType ) );
}
};
// Display a DataSet with three different format providers.
void DisplayDataSet( DataSet^ ds )
{
IFormatProvider^ null = nullptr;
String^ fmt = "{0,-12}{1,20}{2,20}{3,20}";
AverageInfo^ median = gcnew AverageInfo( AverageType::Median );
AverageInfo^ geMean = gcnew AverageInfo( AverageType::GeometricMean );
// Display the dataset elements.
if ( ds->Count > 0 )
{
Console::Write( "\nDataSet: [{0}", ds->Item[ 0 ] );
for ( int iX = 1; iX < ds->Count; iX++ )
Console::Write( ", {0}", ds->Item[ iX ] );
Console::WriteLine( "]\n" );
}
Console::WriteLine( fmt, "Convert::", "Default", "Geometric Mean", "Median" );
Console::WriteLine( fmt, "---------", "-------", "--------------", "------" );
Console::WriteLine( fmt, "ToBoolean", Convert::ToBoolean( ds, null ), Convert::ToBoolean( ds, geMean ), Convert::ToBoolean( ds, median ) );
Console::WriteLine( fmt, "ToByte", Convert::ToByte( ds, null ), Convert::ToByte( ds, geMean ), Convert::ToByte( ds, median ) );
Console::WriteLine( fmt, "ToChar", Convert::ToChar( ds, null ), Convert::ToChar( ds, geMean ), Convert::ToChar( ds, median ) );
Console::WriteLine( "{0,-12}{1,20:yyyy-MM-dd HH:mm:ss}"
"{2,20:yyyy-MM-dd HH:mm:ss}{3,20:yyyy-MM-dd HH:mm:ss}", "ToDateTime", Convert::ToDateTime( ds, null ), Convert::ToDateTime( ds, geMean ), Convert::ToDateTime( ds, median ) );
Console::WriteLine( fmt, "ToDecimal", Convert::ToDecimal( ds, null ), Convert::ToDecimal( ds, geMean ), Convert::ToDecimal( ds, median ) );
Console::WriteLine( fmt, "ToDouble", Convert::ToDouble( ds, null ), Convert::ToDouble( ds, geMean ), Convert::ToDouble( ds, median ) );
Console::WriteLine( fmt, "ToInt16", Convert::ToInt16( ds, null ), Convert::ToInt16( ds, geMean ), Convert::ToInt16( ds, median ) );
Console::WriteLine( fmt, "ToInt32", Convert::ToInt32( ds, null ), Convert::ToInt32( ds, geMean ), Convert::ToInt32( ds, median ) );
Console::WriteLine( fmt, "ToInt64", Convert::ToInt64( ds, null ), Convert::ToInt64( ds, geMean ), Convert::ToInt64( ds, median ) );
Console::WriteLine( fmt, "ToSByte", Convert::ToSByte( ds, null ), Convert::ToSByte( ds, geMean ), Convert::ToSByte( ds, median ) );
Console::WriteLine( fmt, "ToSingle", Convert::ToSingle( ds, null ), Convert::ToSingle( ds, geMean ), Convert::ToSingle( ds, median ) );
Console::WriteLine( fmt, "ToUInt16", Convert::ToUInt16( ds, null ), Convert::ToUInt16( ds, geMean ), Convert::ToUInt16( ds, median ) );
Console::WriteLine( fmt, "ToUInt32", Convert::ToUInt32( ds, null ), Convert::ToUInt32( ds, geMean ), Convert::ToUInt32( ds, median ) );
Console::WriteLine( fmt, "ToUInt64", Convert::ToUInt64( ds, null ), Convert::ToUInt64( ds, geMean ), Convert::ToUInt64( ds, median ) );
}
int main()
{
Console::WriteLine( "This example of the "
"Convert::To<Type>( Object*, IFormatProvider* ) methods "
"\ngenerates the following output. The example "
"displays the values \nreturned by the methods, "
"using several IFormatProvider objects.\n" );
// To call a [ParamArray] method in C++, you cannot just
// list the parameters, you need to build an array.
array<Double>^dataElem = gcnew array<Double>(6);
dataElem[ 0 ] = 10.5;
dataElem[ 1 ] = 22.2;
dataElem[ 2 ] = 45.9;
dataElem[ 3 ] = 88.7;
dataElem[ 4 ] = 156.05;
dataElem[ 5 ] = 297.6;
DataSet^ ds1 = gcnew DataSet( dataElem );
DisplayDataSet( ds1 );
dataElem = gcnew array<Double>(5);
dataElem[ 0 ] = 359999.95;
dataElem[ 1 ] = 425000;
dataElem[ 2 ] = 499999.5;
dataElem[ 3 ] = 775000;
dataElem[ 4 ] = 1695000;
DataSet^ ds2 = gcnew DataSet( dataElem );
DisplayDataSet( ds2 );
}
/*
This example of the Convert::To<Type>( Object*, IFormatProvider* ) methods
generates the following output. The example displays the values
returned by the methods, using several IFormatProvider objects.
DataSet: [10.5, 22.2, 45.9, 88.7, 156.05, 297.6]
Convert:: Default Geometric Mean Median
--------- ------- -------------- ------
ToBoolean True True True
ToByte 103 59 67
ToChar g ; C
ToDateTime 2003-05-13 15:30:23 2003-05-13 15:29:39 2003-05-13 15:29:47
ToDecimal 103.491666666667 59.4332135445164 67.3
ToDouble 103.491666666667 59.4332135445164 67.3
ToInt16 103 59 67
ToInt32 103 59 67
ToInt64 103 59 67
ToSByte 103 59 67
ToSingle 103.4917 59.43321 67.3
ToUInt16 103 59 67
ToUInt32 103 59 67
ToUInt64 103 59 67
DataSet: [359999.95, 425000, 499999.5, 775000, 1695000]
Convert:: Default Geometric Mean Median
--------- ------- -------------- ------
ToBoolean True True True
ToByte 255 255 255
ToChar ? ? ?
ToDateTime 2003-05-22 08:05:19 2003-05-20 22:54:57 2003-05-19 10:21:59
ToDecimal 750999.89 631577.237188435 499999.5
ToDouble 750999.89 631577.237188435 499999.5
ToInt16 32767 32767 32767
ToInt32 751000 631577 500000
ToInt64 751000 631577 500000
ToSByte 127 127 127
ToSingle 750999.9 631577.3 499999.5
ToUInt16 65535 65535 65535
ToUInt32 751000 631577 500000
ToUInt64 751000 631577 500000
*/
C#
using System;
using System.Collections;
// Define the types of averaging available in the class
// implementing IConvertible.
public enum AverageType : short
{
None = 0,
GeometricMean = 1,
ArithmeticMean = 2,
Median = 3
};
// Pass an instance of this class to methods that require an
// IFormatProvider. The class instance determines the type of
// average to calculate.
public class AverageInfo : IFormatProvider
{
protected AverageType AvgType;
// Specify the type of averaging in the constructor.
public AverageInfo( AverageType avgType )
{
this.AvgType = avgType;
}
// This method returns a reference to the containing object
// if an object of AverageInfo type is requested.
public object GetFormat( Type argType )
{
if ( argType == typeof( AverageInfo ) )
return this;
else
return null;
}
// Use this property to set or get the type of averaging.
public AverageType TypeOfAverage
{
get { return this.AvgType; }
set { this.AvgType = value; }
}
}
// This class encapsulates an array of double values and implements
// the IConvertible interface. Most of the IConvertible methods
// return an average of the array elements in one of three types:
// arithmetic mean, geometric mean, or median.
public class DataSet : IConvertible
{
protected ArrayList data;
protected AverageInfo defaultProvider;
// Construct the object and add an initial list of values.
// Create a default format provider.
public DataSet( params double[ ] values )
{
data = new ArrayList( values );
defaultProvider =
new AverageInfo( AverageType.ArithmeticMean );
}
// Add additional values with this method.
public int Add( double value )
{
data.Add( value );
return data.Count;
}
// Get, set, and add values with this indexer property.
public double this[ int index ]
{
get
{
if( index >= 0 && index < data.Count )
return (double)data[ index ];
else
throw new InvalidOperationException(
"[DataSet.get] Index out of range." );
}
set
{
if( index >= 0 && index < data.Count )
data[ index ] = value;
else if( index == data.Count )
data.Add( value );
else
throw new InvalidOperationException(
"[DataSet.set] Index out of range." );
}
}
// This property returns the number of elements in the object.
public int Count
{
get { return data.Count; }
}
// This method calculates the average of the object's elements.
protected double Average( AverageType avgType )
{
double SumProd;
if( data.Count == 0 )
return 0.0;
switch( avgType )
{
case AverageType.GeometricMean:
SumProd = 1.0;
for( int Index = 0; Index < data.Count; Index++ )
SumProd *= (double)data[ Index ];
// This calculation will not fail with negative
// elements.
return Math.Sign( SumProd ) * Math.Pow(
Math.Abs( SumProd ), 1.0 / data.Count );
case AverageType.ArithmeticMean:
SumProd = 0.0;
for( int Index = 0; Index < data.Count; Index++ )
SumProd += (double)data[ Index ];
return SumProd / data.Count;
case AverageType.Median:
if( data.Count % 2 == 0 )
return ( (double)data[ data.Count / 2 ] +
(double)data[ data.Count / 2 - 1 ] ) / 2.0;
else
return (double)data[ data.Count / 2 ];
default:
return 0.0;
}
}
// Get the AverageInfo object from the caller's format provider,
// or use the local default.
protected AverageInfo GetAverageInfo( IFormatProvider provider )
{
AverageInfo avgInfo = null;
if( provider != null )
avgInfo = (AverageInfo)provider.GetFormat(
typeof( AverageInfo ) );
if ( avgInfo == null )
return defaultProvider;
else
return avgInfo;
}
// Calculate the average and limit the range.
protected double CalcNLimitAverage( double min, double max,
IFormatProvider provider )
{
// Get the format provider and calculate the average.
AverageInfo avgInfo = GetAverageInfo( provider );
double avg = Average( avgInfo.TypeOfAverage );
// Limit the range, based on the minimum and maximum values
// for the type.
return avg > max ? max : avg < min ? min : avg;
}
// The following elements are required by IConvertible.
// None of these conversion functions throw exceptions. When
// the data is out of range for the type, the appropriate
// MinValue or MaxValue is used.
public TypeCode GetTypeCode( )
{
return TypeCode.Object;
}
public bool ToBoolean( IFormatProvider provider )
{
// ToBoolean is false if the dataset is empty.
if( data.Count <= 0 )
{
return false;
}
// For median averaging, ToBoolean is true if any
// non-discarded elements are nonzero.
else if( AverageType.Median ==
GetAverageInfo( provider ).TypeOfAverage )
{
if (data.Count % 2 == 0 )
return ( (double)data[ data.Count / 2 ] != 0.0 ||
(double)data[ data.Count / 2 - 1 ] != 0.0 );
else
return (double)data[ data.Count / 2 ] != 0.0;
}
// For arithmetic or geometric mean averaging, ToBoolean is
// true if any element of the dataset is nonzero.
else
{
for( int Index = 0; Index < data.Count; Index++ )
if( (double)data[ Index ] != 0.0 )
return true;
return false;
}
}
public byte ToByte( IFormatProvider provider )
{
return Convert.ToByte( CalcNLimitAverage(
Byte.MinValue, Byte.MaxValue, provider ) );
}
public char ToChar( IFormatProvider provider )
{
return Convert.ToChar( Convert.ToUInt16( CalcNLimitAverage(
Char.MinValue, Char.MaxValue, provider ) ) );
}
// Convert to DateTime by adding the calculated average as
// seconds to the current date and time. A valid DateTime is
// always returned.
public DateTime ToDateTime( IFormatProvider provider )
{
double seconds =
Average( GetAverageInfo( provider ).TypeOfAverage );
try
{
return DateTime.Now.AddSeconds( seconds );
}
catch( ArgumentOutOfRangeException )
{
return seconds < 0.0 ? DateTime.MinValue : DateTime.MaxValue;
}
}
public decimal ToDecimal( IFormatProvider provider )
{
// The Double conversion rounds Decimal.MinValue and
// Decimal.MaxValue to invalid Decimal values, so the
// following limits must be used.
return Convert.ToDecimal( CalcNLimitAverage(
-79228162514264330000000000000.0,
79228162514264330000000000000.0, provider ) );
}
public double ToDouble( IFormatProvider provider )
{
return Average( GetAverageInfo(provider).TypeOfAverage );
}
public short ToInt16( IFormatProvider provider )
{
return Convert.ToInt16( CalcNLimitAverage(
Int16.MinValue, Int16.MaxValue, provider ) );
}
public int ToInt32( IFormatProvider provider )
{
return Convert.ToInt32( CalcNLimitAverage(
Int32.MinValue, Int32.MaxValue, provider ) );
}
public long ToInt64( IFormatProvider provider )
{
// The Double conversion rounds Int64.MinValue and
// Int64.MaxValue to invalid Int64 values, so the following
// limits must be used.
return Convert.ToInt64( CalcNLimitAverage(
-9223372036854775000, 9223372036854775000, provider ) );
}
public SByte ToSByte( IFormatProvider provider )
{
return Convert.ToSByte( CalcNLimitAverage(
SByte.MinValue, SByte.MaxValue, provider ) );
}
public float ToSingle( IFormatProvider provider )
{
return Convert.ToSingle( CalcNLimitAverage(
Single.MinValue, Single.MaxValue, provider ) );
}
public UInt16 ToUInt16( IFormatProvider provider )
{
return Convert.ToUInt16( CalcNLimitAverage(
UInt16.MinValue, UInt16.MaxValue, provider ) );
}
public UInt32 ToUInt32( IFormatProvider provider )
{
return Convert.ToUInt32( CalcNLimitAverage(
UInt32.MinValue, UInt32.MaxValue, provider ) );
}
public UInt64 ToUInt64( IFormatProvider provider )
{
// The Double conversion rounds UInt64.MaxValue to an invalid
// UInt64 value, so the following limit must be used.
return Convert.ToUInt64( CalcNLimitAverage(
0, 18446744073709550000.0, provider ) );
}
public object ToType( Type conversionType,
IFormatProvider provider )
{
return Convert.ChangeType( Average(
GetAverageInfo( provider ).TypeOfAverage ),
conversionType );
}
public string ToString( IFormatProvider provider )
{
AverageType avgType = GetAverageInfo( provider ).TypeOfAverage;
return String.Format( "( {0}: {1:G10} )", avgType,
Average( avgType ) );
}
}
class IConvertibleProviderDemo
{
// Display a DataSet with three different format providers.
public static void DisplayDataSet( DataSet ds )
{
string fmt = "{0,-12}{1,20}{2,20}{3,20}";
AverageInfo median = new AverageInfo( AverageType.Median );
AverageInfo geMean =
new AverageInfo( AverageType.GeometricMean );
// Display the dataset elements.
if( ds.Count > 0 )
{
Console.Write( "\nDataSet: [{0}", ds[ 0 ] );
for( int iX = 1; iX < ds.Count; iX++ )
Console.Write( ", {0}", ds[ iX ] );
Console.WriteLine( "]\n" );
}
Console.WriteLine( fmt, "Convert.", "Default",
"Geometric Mean", "Median");
Console.WriteLine( fmt, "--------", "-------",
"--------------", "------");
Console.WriteLine( fmt, "ToBoolean",
Convert.ToBoolean( ds, null ),
Convert.ToBoolean( ds, geMean ),
Convert.ToBoolean( ds, median ) );
Console.WriteLine( fmt, "ToByte",
Convert.ToByte( ds, null ),
Convert.ToByte( ds, geMean ),
Convert.ToByte( ds, median ) );
Console.WriteLine( fmt, "ToChar",
Convert.ToChar( ds, null ),
Convert.ToChar( ds, geMean ),
Convert.ToChar( ds, median ) );
Console.WriteLine( "{0,-12}{1,20:yyyy-MM-dd HH:mm:ss}" +
"{2,20:yyyy-MM-dd HH:mm:ss}{3,20:yyyy-MM-dd HH:mm:ss}",
"ToDateTime", Convert.ToDateTime( ds, null ),
Convert.ToDateTime( ds, geMean ),
Convert.ToDateTime( ds, median ) );
Console.WriteLine( fmt, "ToDecimal",
Convert.ToDecimal( ds, null ),
Convert.ToDecimal( ds, geMean ),
Convert.ToDecimal( ds, median ) );
Console.WriteLine( fmt, "ToDouble",
Convert.ToDouble( ds, null ),
Convert.ToDouble( ds, geMean ),
Convert.ToDouble( ds, median ) );
Console.WriteLine( fmt, "ToInt16",
Convert.ToInt16( ds, null ),
Convert.ToInt16( ds, geMean ),
Convert.ToInt16( ds, median ) );
Console.WriteLine( fmt, "ToInt32",
Convert.ToInt32( ds, null ),
Convert.ToInt32( ds, geMean ),
Convert.ToInt32( ds, median ) );
Console.WriteLine( fmt, "ToInt64",
Convert.ToInt64( ds, null ),
Convert.ToInt64( ds, geMean ),
Convert.ToInt64( ds, median ) );
Console.WriteLine( fmt, "ToSByte",
Convert.ToSByte( ds, null ),
Convert.ToSByte( ds, geMean ),
Convert.ToSByte( ds, median ) );
Console.WriteLine( fmt, "ToSingle",
Convert.ToSingle( ds, null ),
Convert.ToSingle( ds, geMean ),
Convert.ToSingle( ds, median ) );
Console.WriteLine( fmt, "ToUInt16",
Convert.ToUInt16( ds, null ),
Convert.ToUInt16( ds, geMean ),
Convert.ToUInt16( ds, median ) );
Console.WriteLine( fmt, "ToUInt32",
Convert.ToUInt32( ds, null ),
Convert.ToUInt32( ds, geMean ),
Convert.ToUInt32( ds, median ) );
Console.WriteLine( fmt, "ToUInt64",
Convert.ToUInt64( ds, null ),
Convert.ToUInt64( ds, geMean ),
Convert.ToUInt64( ds, median ) );
}
public static void Main( )
{
Console.WriteLine( "This example of " +
"the Convert.To<Type>( object, IFormatProvider ) methods " +
"\ngenerates the following output. The example " +
"displays the values \nreturned by the methods, " +
"using several IFormatProvider objects.\n" );
DataSet ds1 = new DataSet(
10.5, 22.2, 45.9, 88.7, 156.05, 297.6 );
DisplayDataSet( ds1 );
DataSet ds2 = new DataSet(
359999.95, 425000, 499999.5, 775000, 1695000 );
DisplayDataSet( ds2 );
}
}
/*
This example of the Convert.To<Type>( object, IFormatProvider ) methods
generates the following output. The example displays the values
returned by the methods, using several IFormatProvider objects.
DataSet: [10.5, 22.2, 45.9, 88.7, 156.05, 297.6]
Convert. Default Geometric Mean Median
-------- ------- -------------- ------
ToBoolean True True True
ToByte 103 59 67
ToChar g ; C
ToDateTime 2003-05-13 15:04:12 2003-05-13 15:03:28 2003-05-13 15:03:35
ToDecimal 103.491666666667 59.4332135445164 67.3
ToDouble 103.491666666667 59.4332135445164 67.3
ToInt16 103 59 67
ToInt32 103 59 67
ToInt64 103 59 67
ToSByte 103 59 67
ToSingle 103.4917 59.43321 67.3
ToUInt16 103 59 67
ToUInt32 103 59 67
ToUInt64 103 59 67
DataSet: [359999.95, 425000, 499999.5, 775000, 1695000]
Convert. Default Geometric Mean Median
-------- ------- -------------- ------
ToBoolean True True True
ToByte 255 255 255
ToChar ? ? ?
ToDateTime 2003-05-22 07:39:08 2003-05-20 22:28:45 2003-05-19 09:55:48
ToDecimal 750999.89 631577.237188435 499999.5
ToDouble 750999.89 631577.237188435 499999.5
ToInt16 32767 32767 32767
ToInt32 751000 631577 500000
ToInt64 751000 631577 500000
ToSByte 127 127 127
ToSingle 750999.9 631577.3 499999.5
ToUInt16 65535 65535 65535
ToUInt32 751000 631577 500000
ToUInt64 751000 631577 500000
*/
open System
open System.Collections
// Define the types of averaging available in the class
// implementing IConvertible.
type AverageType =
| None = 0s
| GeometricMean = 1s
| ArithmeticMean = 2s
| Median = 3s
// Pass an instance of this class to methods that require an
// IFormatProvider. The class instance determines the type of
// average to calculate.
[<AllowNullLiteral>]
type AverageInfo(avgType: AverageType) =
// Use this property to set or get the type of averaging.
member val TypeOfAverage = avgType with get, set
interface IFormatProvider with
// This method returns a reference to the containing object
// if an object of AverageInfo type is requested.
member this.GetFormat(argType: Type) =
if argType = typeof<AverageInfo> then
this
else
null
// This class encapsulates an array of double values and implements
// the IConvertible interface. Most of the IConvertible methods
// an average of the array elements in one of three types:
// arithmetic mean, geometric mean, or median.
type DataSet([<ParamArray>] values: double[]) =
let data = ResizeArray values
let defaultProvider =
AverageInfo AverageType.ArithmeticMean
// Add additional values with this method.
member _.Add(value: double) =
data.Add value
data.Count
// Get, set, and add values with this indexer property.
member _.Item
with get (index) =
if index >= 0 && index < data.Count then
data[index]
else
raise (InvalidOperationException "[DataSet.get] Index out of range.")
and set index value =
if index >= 0 && index < data.Count then
data[index] <- value
elif index = data.Count then
data.Add value
else
raise (InvalidOperationException "[DataSet.set] Index out of range.")
// This property returns the number of elements in the object.
member _.Count =
data.Count
// This method calculates the average of the object's elements.
member _.Average(avgType: AverageType) =
if data.Count = 0 then
0.0
else
match avgType with
| AverageType.GeometricMean ->
let sumProd =
Seq.reduce ( * ) data
// This calculation will not fail with negative
// elements.
(sign sumProd |> float) * Math.Pow(abs sumProd, 1.0 / (float data.Count))
| AverageType.ArithmeticMean ->
Seq.average data
| AverageType.Median ->
if data.Count % 2 = 0 then
(data[data.Count / 2] + data[data.Count / 2 - 1]) / 2.0
else
data[ data.Count / 2]
| _ ->
0.0
// Get the AverageInfo object from the caller's format provider,
// or use the local default.
member _.GetAverageInfo(provider: IFormatProvider) =
let avgInfo =
if provider <> null then
provider.GetFormat typeof<AverageInfo> :?> AverageInfo
else
null
if avgInfo = null then
defaultProvider
else
avgInfo
// Calculate the average and limit the range.
member this.CalcNLimitAverage(min: double, max: double, provider: IFormatProvider) =
// Get the format provider and calculate the average.
let avgInfo = this.GetAverageInfo provider
let avg = this.Average avgInfo.TypeOfAverage
// Limit the range, based on the minimum and maximum values
// for the type.
if avg > max then max elif avg < min then min else avg
// The following elements are required by IConvertible.
interface IConvertible with
// None of these conversion functions throw exceptions. When
// the data is out of range for the type, the appropriate
// MinValue or MaxValue is used.
member _.GetTypeCode() =
TypeCode.Object
member this.ToBoolean(provider: IFormatProvider) =
// ToBoolean is false if the dataset is empty.
if data.Count <= 0 then
false
// For median averaging, ToBoolean is true if any
// non-discarded elements are nonzero.
elif AverageType.Median = this.GetAverageInfo(provider).TypeOfAverage then
if data.Count % 2 = 0 then
(data[data.Count / 2] <> 0.0 || data[data.Count / 2 - 1] <> 0.0)
else
data[data.Count / 2] <> 0.0
// For arithmetic or geometric mean averaging, ToBoolean is
// true if any element of the dataset is nonzero.
else
Seq.exists (fun x -> x <> 0.0) data
member this.ToByte(provider: IFormatProvider) =
Convert.ToByte(this.CalcNLimitAverage(float Byte.MinValue, float Byte.MaxValue, provider) )
member this.ToChar(provider: IFormatProvider) =
Convert.ToChar(Convert.ToUInt16(this.CalcNLimitAverage(float Char.MinValue, float Char.MaxValue, provider) ) )
// Convert to DateTime by adding the calculated average as
// seconds to the current date and time. A valid DateTime is
// always returned.
member this.ToDateTime(provider: IFormatProvider) =
let seconds = this.Average(this.GetAverageInfo(provider).TypeOfAverage)
try
DateTime.Now.AddSeconds seconds
with :? ArgumentOutOfRangeException ->
if seconds < 0.0 then DateTime.MinValue else DateTime.MaxValue
member this.ToDecimal(provider: IFormatProvider) =
// The Double conversion rounds Decimal.MinValue and
// Decimal.MaxValue to invalid Decimal values, so the
// following limits must be used.
Convert.ToDecimal(this.CalcNLimitAverage(-79228162514264330000000000000.0, 79228162514264330000000000000.0, provider) )
member this.ToDouble(provider: IFormatProvider) =
this.Average(this.GetAverageInfo(provider).TypeOfAverage)
member this.ToInt16(provider: IFormatProvider) =
Convert.ToInt16(this.CalcNLimitAverage(float Int16.MinValue, float Int16.MaxValue, provider) )
member this.ToInt32(provider: IFormatProvider) =
Convert.ToInt32(this.CalcNLimitAverage(Int32.MinValue, Int32.MaxValue, provider) )
member this.ToInt64(provider: IFormatProvider) =
// The Double conversion rounds Int64.MinValue and
// Int64.MaxValue to invalid Int64 values, so the following
// limits must be used.
Convert.ToInt64(this.CalcNLimitAverage(-9223372036854775000., 9223372036854775000., provider) )
member this.ToSByte(provider: IFormatProvider) =
Convert.ToSByte(this.CalcNLimitAverage(float SByte.MinValue, float SByte.MaxValue, provider) )
member this.ToSingle(provider: IFormatProvider) =
Convert.ToSingle(this.CalcNLimitAverage(float Single.MinValue, float Single.MaxValue, provider) )
member this.ToUInt16(provider: IFormatProvider) =
Convert.ToUInt16(this.CalcNLimitAverage(float UInt16.MinValue, float UInt16.MaxValue, provider) )
member this.ToUInt32(provider: IFormatProvider) =
Convert.ToUInt32(this.CalcNLimitAverage(float UInt32.MinValue, float UInt32.MaxValue, provider) )
member this.ToUInt64(provider: IFormatProvider) =
// The Double conversion rounds UInt64.MaxValue to an invalid
// UInt64 value, so the following limit must be used.
Convert.ToUInt64(this.CalcNLimitAverage(0, 18446744073709550000.0, provider) )
member this.ToType(conversionType: Type, provider: IFormatProvider) =
Convert.ChangeType(this.Average(this.GetAverageInfo(provider).TypeOfAverage), conversionType)
member this.ToString(provider: IFormatProvider) =
let avgType = this.GetAverageInfo(provider).TypeOfAverage
$"( {avgType}: {this.Average avgType:G10} )"
// Display a DataSet with three different format providers.
let displayDataSet (ds: DataSet) =
let fmt obj1 obj2 obj3 obj4 = printfn $"{obj1,-12}{obj2,20}{obj3,20}{obj4,20}"
let median = AverageInfo AverageType.Median
let geMean =
AverageInfo AverageType.GeometricMean
// Display the dataset elements.
if ds.Count > 0 then
printf $"\nDataSet: [{ds[0]}"
for i = 1 to ds.Count - 1 do
printf $", {ds[i]}"
printfn "]\n"
fmt "Convert." "Default" "Geometric Mean" "Median"
fmt "--------" "-------" "--------------" "------"
fmt "ToBoolean"
(Convert.ToBoolean(ds, null))
(Convert.ToBoolean(ds, geMean))
(Convert.ToBoolean(ds, median))
fmt "ToByte"
(Convert.ToByte(ds, null))
(Convert.ToByte(ds, geMean))
(Convert.ToByte(ds, median))
fmt "ToChar"
(Convert.ToChar(ds, null))
(Convert.ToChar(ds, geMean))
(Convert.ToChar(ds, median))
printfn $"""{"ToDateTime",-12}{Convert.ToDateTime(ds, null).ToString "20:yyyy-MM-dd HH:mm:ss"}{Convert.ToDateTime(ds, geMean).ToString "20:yyyy-MM-dd HH:mm:ss"}{Convert.ToDateTime(ds, median).ToString "20:yyyy-MM-dd HH:mm:ss"}"""
fmt "ToDecimal"
(Convert.ToDecimal(ds, null))
(Convert.ToDecimal(ds, geMean))
(Convert.ToDecimal(ds, median))
fmt "ToDouble"
(Convert.ToDouble(ds, null))
(Convert.ToDouble(ds, geMean))
(Convert.ToDouble(ds, median))
fmt "ToInt16"
(Convert.ToInt16(ds, null))
(Convert.ToInt16(ds, geMean))
(Convert.ToInt16(ds, median))
fmt "ToInt32"
(Convert.ToInt32(ds, null))
(Convert.ToInt32(ds, geMean))
(Convert.ToInt32(ds, median))
fmt "ToInt64"
(Convert.ToInt64(ds, null))
(Convert.ToInt64(ds, geMean))
(Convert.ToInt64(ds, median))
fmt "ToSByte"
(Convert.ToSByte(ds, null))
(Convert.ToSByte(ds, geMean))
(Convert.ToSByte(ds, median))
fmt "ToSingle"
(Convert.ToSingle(ds, null))
(Convert.ToSingle(ds, geMean))
(Convert.ToSingle(ds, median))
fmt "ToUInt16"
(Convert.ToUInt16(ds, null))
(Convert.ToUInt16(ds, geMean))
(Convert.ToUInt16(ds, median))
fmt "ToUInt32"
(Convert.ToUInt32(ds, null))
(Convert.ToUInt32(ds, geMean))
(Convert.ToUInt32(ds, median))
fmt "ToUInt64"
(Convert.ToUInt64(ds, null))
(Convert.ToUInt64(ds, geMean))
(Convert.ToUInt64(ds, median))
printfn
"""This example of the Convert.To<Type>( object, IFormatprovider) methods
generates the following output. The example displays the values
returned by the methods, using several IFormatProvider objects.
"""
let ds1 = DataSet(10.5, 22.2, 45.9, 88.7, 156.05, 297.6)
displayDataSet ds1
let ds2 = DataSet(359999.95, 425000, 499999.5, 775000, 1695000)
displayDataSet ds2
// This example of the Convert.To<Type>( object, IFormatprovider) methods
// generates the following output. The example displays the values
// returned by the methods, using several IFormatProvider objects.
//
// DataSet: [10.5, 22.2, 45.9, 88.7, 156.05, 297.6]
//
// Convert. Default Geometric Mean Median
// -------- ------- -------------- ------
// ToBoolean True True True
// ToByte 103 59 67
// ToChar g ; C
// ToDateTime 2003-05-13 15:04:12 2003-05-13 15:03:28 2003-05-13 15:03:35
// ToDecimal 103.491666666667 59.4332135445164 67.3
// ToDouble 103.491666666667 59.4332135445164 67.3
// ToInt16 103 59 67
// ToInt32 103 59 67
// ToInt64 103 59 67
// ToSByte 103 59 67
// ToSingle 103.4917 59.43321 67.3
// ToUInt16 103 59 67
// ToUInt32 103 59 67
// ToUInt64 103 59 67
//
// DataSet: [359999.95, 425000, 499999.5, 775000, 1695000]
//
// Convert. Default Geometric Mean Median
// -------- ------- -------------- ------
// ToBoolean True True True
// ToByte 255 255 255
// ToChar ? ? ?
// ToDateTime 2003-05-22 07:39:08 2003-05-20 22:28:45 2003-05-19 09:55:48
// ToDecimal 750999.89 631577.237188435 499999.5
// ToDouble 750999.89 631577.237188435 499999.5
// ToInt16 32767 32767 32767
// ToInt32 751000 631577 500000
// ToInt64 751000 631577 500000
// ToSByte 127 127 127
// ToSingle 750999.9 631577.3 499999.5
// ToUInt16 65535 65535 65535
// ToUInt32 751000 631577 500000
// ToUInt64 751000 631577 500000
Imports System.Collections
Module IConvertibleProviderDemo
' Define the types of averaging available in the class
' implementing IConvertible.
Enum AverageType as Short
None = 0
GeometricMean = 1
ArithmeticMean = 2
Median = 3
End Enum
' Pass an instance of this class to methods that require an
' IFormatProvider. The class instance determines the type of
' average to calculate.
Public Class AverageInfo
Implements IFormatProvider
Protected AvgType As AverageType
' Specify the type of averaging in the constructor.
Public Sub New( avgType As AverageType )
Me.AvgType = avgType
End Sub
' This method returns a reference to the containing object
' if an object of AverageInfo type is requested.
Public Function GetFormat( argType As Type ) As Object _
Implements IFormatProvider.GetFormat
If argType Is GetType( AverageInfo ) Then
Return Me
Else
Return Nothing
End If
End Function
' Use this property to set or get the type of averaging.
Public Property TypeOfAverage( ) As AverageType
Get
Return Me.AvgType
End Get
Set( ByVal value as AverageType )
Me.AvgType = value
End Set
End Property
End Class
' This class encapsulates an array of Double values and implements
' the IConvertible interface. Most of the IConvertible methods
' return an average of the array elements in one of three types:
' arithmetic mean, geometric mean, or median.
Public Class DataSet
Implements IConvertible
Protected data As ArrayList
Protected defaultProvider As AverageInfo
' Construct the object and add an initial list of values.
' Create a default format provider.
Public Sub New( ParamArray values( ) As Double )
data = New ArrayList( values )
defaultProvider = New AverageInfo( _
AverageType.ArithmeticMean )
End Sub
' Add additional values with this method.
Public Function Add( value As Double ) As Integer
data.Add( value )
Return data.Count
End Function
' Get, set, and add values with this indexer property.
Default Public Property Item(index As Integer) As Double
Get
If index >= 0 AndAlso index < data.Count Then
Return System.Convert.ToDouble( data( index ) )
Else
Throw New InvalidOperationException( _
"[DataSet.get] Index out of range." )
End If
End Get
Set
If index >= 0 AndAlso index < data.Count Then
data( index ) = value
ElseIf index = data.Count Then
data.Add( value )
Else
Throw New InvalidOperationException( _
"[DataSet.set] Index out of range." )
End If
End Set
End Property
' This property returns the number of elements in the object.
Public ReadOnly Property Count( ) As Integer
Get
Return data.Count
End Get
End Property
' This method calculates the average of the object's elements.
Protected Function Average( ByVal avgType As AverageType ) As Double
Dim SumProd As Double
Dim Index As Integer
If data.Count = 0 Then Return 0.0
Select Case avgType
Case AverageType.GeometricMean
SumProd = 1.0
For Index = 0 To data.Count - 1
SumProd *= data( Index )
Next Index
' This calculation will not fail with negative
' elements.
Return Math.Sign( SumProd ) * Math.Pow( _
Math.Abs( SumProd ), 1.0 / data.Count )
Case AverageType.ArithmeticMean
SumProd = 0.0
For Index = 0 To data.Count - 1
SumProd += data( Index )
Next Index
Return SumProd / data.Count
Case AverageType.Median
If data.Count Mod 2 = 0 Then
Return ( data( data.Count \ 2 ) + _
data( data.Count \ 2 - 1 ) ) / 2.0
Else
Return data( data.Count \ 2 )
End If
End Select
End Function
' Get the AverageInfo object from the caller's format
' provider, or use the local default.
Protected Function GetAverageInfo( _
provider As IFormatProvider ) As AverageInfo
Dim avgInfo As AverageInfo = Nothing
If Not provider Is Nothing Then
avgInfo = provider.GetFormat( GetType( AverageInfo ) )
End If
Return IIf( avgInfo Is Nothing, defaultProvider, avgInfo )
End Function
' Calculate the average and limit the range.
Protected Function CalcNLimitAverage( min As Double, _
max As Double, provider as IFormatProvider ) As Double
' Get the format provider and calculate the average.
Dim avgInfo As AverageInfo = GetAverageInfo( provider )
Dim avg As Double = Average( avgInfo.TypeOfAverage )
' Limit the range, based on the minimum and maximum values
' for the type.
Return IIf( avg > max, max, IIf( avg < min, min, avg ) )
End Function
' The following elements are required by IConvertible.
' None of these conversion functions throw exceptions. When
' the data is out of range for the type, the appropriate
' MinValue or MaxValue is used.
Public Function GetTypeCode( ) As TypeCode _
Implements IConvertible.GetTypeCode
Return TypeCode.Object
End Function
Function ToBoolean( ByVal provider As IFormatProvider ) As _
Boolean Implements IConvertible.ToBoolean
' ToBoolean is false if the dataset is empty.
If data.Count <= 0 Then
Return False
' For median averaging, ToBoolean is true if any
' non-discarded elements are nonzero.
ElseIf AverageType.Median = _
GetAverageInfo( provider ).TypeOfAverage Then
If data.Count Mod 2 = 0 Then
Return ( data( data.Count \ 2 ) <> 0.0 Or _
data( data.Count \ 2 - 1 ) <> 0.0 )
Else
Return data( data.Count \ 2 ) <> 0.0
End If
' For arithmetic or geometric mean averaging, ToBoolean is
' true if any element of the dataset is nonzero.
Else
Dim Index As Integer
For Index = 0 To data.Count - 1
If data( Index ) <> 0.0 Then Return True
Next Index
Return False
End If
End Function
Function ToByte( ByVal provider As IFormatProvider ) As Byte _
Implements IConvertible.ToByte
Return Convert.ToByte( CalcNLimitAverage( _
Byte.MinValue, Byte.MaxValue, provider ) )
End Function
Function ToChar( ByVal provider As IFormatProvider ) As Char _
Implements IConvertible.ToChar
Return Convert.ToChar( Convert.ToUInt16( _
CalcNLimitAverage( 0.0, &HFFFF, provider ) ) )
End Function
' Convert to DateTime by adding the calculated average as
' seconds to the current date and time. A valid DateTime is
' always returned.
Function ToDateTime( ByVal provider As IFormatProvider ) As _
DateTime Implements IConvertible.ToDateTime
Dim seconds As Double = Average( _
GetAverageInfo( provider ).TypeOfAverage )
Try
Return DateTime.Now.AddSeconds( seconds )
Catch ex As ArgumentOutOfRangeException
Return IIf( seconds < 0.0, DateTime.MinValue, _
DateTime.MaxValue )
End Try
End Function
Function ToDecimal( ByVal provider As IFormatProvider ) As _
Decimal Implements IConvertible.ToDecimal
' The Double conversion rounds Decimal.MinValue and
' Decimal.MaxValue to invalid Decimal values, so the
' following limits must be used.
Return Convert.ToDecimal( CalcNLimitAverage( _
-79228162514264330000000000000.0, _
79228162514264330000000000000.0, provider ) )
End Function
Function ToDouble( ByVal provider As IFormatProvider) As _
Double Implements IConvertible.ToDouble
Return Average( GetAverageInfo( provider ).TypeOfAverage )
End Function
Function ToInt16( ByVal provider As IFormatProvider ) As _
Short Implements IConvertible.ToInt16
Return Convert.ToInt16( CalcNLimitAverage( _
Int16.MinValue, Int16.MaxValue, provider ) )
End Function
Function ToInt32( ByVal provider As IFormatProvider ) As _
Integer Implements IConvertible.ToInt32
Return Convert.ToInt32( CalcNLimitAverage( _
Int32.MinValue, Int32.MaxValue, provider ) )
End Function
Function ToInt64( ByVal provider As IFormatProvider ) As Long _
Implements IConvertible.ToInt64
' The Double conversion rounds Int64.MinValue and
' Int64.MaxValue to invalid Long values, so the following
' limits must be used.
Return Convert.ToInt64( CalcNLimitAverage( _
-9223372036854775000, 9223372036854775000, provider ) )
End Function
Function ToSByte( ByVal provider As IFormatProvider ) As _
SByte Implements IConvertible.ToSByte
' SByte.MinValue and SByte.MaxValue are not defined in
' Visual Basic.
Return Convert.ToSByte( CalcNLimitAverage( _
-128, 127, provider ) )
End Function
Function ToSingle( ByVal provider As IFormatProvider ) As _
Single Implements IConvertible.ToSingle
Return Convert.ToSingle( CalcNLimitAverage( _
Single.MinValue, Single.MaxValue, provider ) )
End Function
Function ToUInt16( ByVal provider As IFormatProvider ) As _
UInt16 Implements IConvertible.ToUInt16
' UInt16.MinValue and UInt16.MaxValue are not defined in
' Visual Basic.
Return Convert.ToUInt16( CalcNLimitAverage( _
0, &HFFFF, provider ) )
End Function
Function ToUInt32( ByVal provider As IFormatProvider ) As _
UInt32 Implements IConvertible.ToUInt32
' UInt32.MinValue and UInt32.MaxValue are not defined in
' Visual Basic.
Return Convert.ToUInt32( CalcNLimitAverage( _
0, 4294967295, provider ) )
End Function
Function ToUInt64( ByVal provider As IFormatProvider ) As _
UInt64 Implements IConvertible.ToUInt64
' UInt64.MinValue and UInt64.MaxValue are not defined in
' Visual Basic. The Double conversion would have rounded
' UInt64.MaxValue, so the following limit must be used.
Return Convert.ToUInt64( CalcNLimitAverage( _
0, 18446744073709550000.0, provider ) )
End Function
Function ToType( ByVal conversionType As Type, _
ByVal provider As IFormatProvider) As Object _
Implements IConvertible.ToType
Return Convert.ChangeType( Average( GetAverageInfo( _
provider ).TypeOfAverage ), conversionType )
End Function
Overloads Function ToString( ByVal provider As IFormatProvider _
) As String Implements IConvertible.ToString
Dim avgType as AverageType = _
GetAverageInfo( provider ).TypeOfAverage
Return String.Format( "( {0}: {1:G10} )", avgType, _
Average( avgType ) )
End Function
End Class
' Display a DataSet with three different format providers.
Sub DisplayDataSet( ds As DataSet )
Dim fmt As String = "{0,-12}{1,20}{2,20}{3,20}"
Dim median As AverageInfo = New AverageInfo( AverageType.Median )
Dim geMean As AverageInfo = _
New AverageInfo( AverageType.GeometricMean )
Dim iX As Integer
' Display the dataset elements.
If ds.Count > 0 Then
Console.Write( vbCrLf & "DataSet: [{0}", ds( 0 ) )
For iX = 1 To ds.Count - 1
Console.Write( ", {0}", ds( iX ) )
Next iX
Console.WriteLine( "]" & vbCrLf )
End If
Console.WriteLine( fmt, "Convert.", "Default", _
"Geometric Mean", "Median" )
Console.WriteLine( fmt, "--------", "-------", _
"--------------", "------" )
Console.WriteLine( fmt, "ToBoolean", _
Convert.ToBoolean( ds, Nothing ), _
Convert.ToBoolean( ds, geMean ), _
Convert.ToBoolean( ds, median ) )
Console.WriteLine( fmt, "ToByte", _
Convert.ToByte( ds, Nothing ), _
Convert.ToByte( ds, geMean ), _
Convert.ToByte( ds, median ) )
Console.WriteLine( fmt, "ToChar", _
Convert.ToChar( ds, Nothing ), _
Convert.ToChar( ds, geMean ), _
Convert.ToChar( ds, median ) )
Console.WriteLine( "{0,-12}{1,20:yyyy-MM-dd HH:mm:ss}" & _
"{2,20:yyyy-MM-dd HH:mm:ss}{3,20:yyyy-MM-dd HH:mm:ss}", _
"ToDateTime", Convert.ToDateTime( ds, Nothing ), _
Convert.ToDateTime( ds, geMean ), _
Convert.ToDateTime( ds, median ) )
Console.WriteLine( fmt, "ToDecimal", _
Convert.ToDecimal( ds, Nothing ), _
Convert.ToDecimal( ds, geMean ), _
Convert.ToDecimal( ds, median ) )
Console.WriteLine( fmt, "ToDouble", _
Convert.ToDouble( ds, Nothing ), _
Convert.ToDouble( ds, geMean ), _
Convert.ToDouble( ds, median ) )
Console.WriteLine( fmt, "ToInt16", _
Convert.ToInt16( ds, Nothing ), _
Convert.ToInt16( ds, geMean ), _
Convert.ToInt16( ds, median ) )
Console.WriteLine( fmt, "ToInt32", _
Convert.ToInt32( ds, Nothing ), _
Convert.ToInt32( ds, geMean ), _
Convert.ToInt32( ds, median ) )
Console.WriteLine( fmt, "ToInt64", _
Convert.ToInt64( ds, Nothing ), _
Convert.ToInt64( ds, geMean ), _
Convert.ToInt64( ds, median ) )
Console.WriteLine( fmt, "ToSByte", _
Convert.ToSByte( ds, Nothing ), _
Convert.ToSByte( ds, geMean ), _
Convert.ToSByte( ds, median ) )
Console.WriteLine( fmt, "ToSingle", _
Convert.ToSingle( ds, Nothing ), _
Convert.ToSingle( ds, geMean ), _
Convert.ToSingle( ds, median ) )
Console.WriteLine( fmt, "ToUInt16", _
Convert.ToUInt16( ds, Nothing ), _
Convert.ToUInt16( ds, geMean ), _
Convert.ToUInt16( ds, median ) )
Console.WriteLine( fmt, "ToUInt32", _
Convert.ToUInt32( ds, Nothing ), _
Convert.ToUInt32( ds, geMean ), _
Convert.ToUInt32( ds, median ) )
Console.WriteLine( fmt, "ToUInt64", _
Convert.ToUInt64( ds, Nothing ), _
Convert.ToUInt64( ds, geMean ), _
Convert.ToUInt64( ds, median ) )
End Sub
Sub Main( )
Console.WriteLine( _
"This example of the Convert.To<Type>( Object, " & _
"IFormatProvider ) methods " & vbCrLf & "generates " & _
"the following output. The example displays the " & _
"values " & vbCrLf & "returned by the methods, " & _
"using several IFormatProvider objects." & vbCrLf )
Dim ds1 As New DataSet( 10.5, 22.2, 45.9, 88.7, 156.05, 297.6 )
DisplayDataSet( ds1 )
Dim ds2 As New DataSet( _
359999.95, 425000, 499999.5, 775000, 1695000 )
DisplayDataSet( ds2 )
End Sub
End Module
' This example of the Convert.To<Type>( Object, IFormatProvider ) methods
' generates the following output. The example displays the values
' returned by the methods, using several IFormatProvider objects.
'
' DataSet: [10.5, 22.2, 45.9, 88.7, 156.05, 297.6]
'
' Convert. Default Geometric Mean Median
' -------- ------- -------------- ------
' ToBoolean True True True
' ToByte 103 59 67
' ToChar g ; C
' ToDateTime 2003-05-13 14:52:53 2003-05-13 14:52:09 2003-05-13 14:52:17
' ToDecimal 103.491666666667 59.4332135445164 67.3
' ToDouble 103.491666666667 59.4332135445164 67.3
' ToInt16 103 59 67
' ToInt32 103 59 67
' ToInt64 103 59 67
' ToSByte 103 59 67
' ToSingle 103.4917 59.43321 67.3
' ToUInt16 103 59 67
' ToUInt32 103 59 67
' ToUInt64 103 59 67
'
' DataSet: [359999.95, 425000, 499999.5, 775000, 1695000]
'
' Convert. Default Geometric Mean Median
' -------- ------- -------------- ------
' ToBoolean True True True
' ToByte 255 255 255
' ToChar ? ? ?
' ToDateTime 2003-05-22 07:27:49 2003-05-20 22:17:27 2003-05-19 09:44:29
' ToDecimal 750999.89 631577.237188435 499999.5
' ToDouble 750999.89 631577.237188435 499999.5
' ToInt16 32767 32767 32767
' ToInt32 751000 631577 500000
' ToInt64 751000 631577 500000
' ToSByte 127 127 127
' ToSingle 750999.9 631577.3 499999.5
' ToUInt16 65535 65535 65535
' ToUInt32 751000 631577 500000
' ToUInt64 751000 631577 500000
注解
provider 使用户能够指定有关 的内容 value的区域性特定转换信息。 基类型忽略 provider 参数;但是，如果 value 是实现 接口的用户定义类型，可以使用 参数 IConvertible 。
另请参阅
适用于
.NET 9 和其他版本
| 产品 | 版本 |
|---|---|
| .NET | Core 1.0, Core 1.1, Core 2.0, Core 2.1, Core 2.2, Core 3.0, Core 3.1, 5, 6, 7, 8, 9 |
| .NET Framework | 1.1, 2.0, 3.0, 3.5, 4.0, 4.5, 4.5.1, 4.5.2, 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2, 4.8, 4.8.1 |
| .NET Standard | 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 2.0, 2.1 |
| UWP | 10.0 |
- Source:
- Convert.cs
- Source:
- Convert.cs
- Source:
- Convert.cs
重要
此 API 不符合 CLS。
将指定的 64 位无符号整数的值转换为等效的布尔值。
public:
static bool ToBoolean(System::UInt64 value);C#
[System.CLSCompliant(false)]
public static bool ToBoolean (ulong value);[<System.CLSCompliant(false)>]
static member ToBoolean : uint64 -> boolPublic Shared Function ToBoolean (value As ULong) As Boolean参数
- value
- UInt64
要转换的 64 位无符号整数。
返回
如果 true 不为零，则为 value；否则，为 false。
- 属性
示例
以下示例将值的数组 UInt64 转换为 Boolean 值。
array<UInt64>^ numbers = gcnew array<UInt64> { UInt64::MinValue, 6121, 403890774, UInt64::MaxValue };
bool result;
for each (UInt64 number in numbers)
{
result = Convert::ToBoolean(number);
Console::WriteLine("{0,-26:N0} --> {1}", number, result);
}
// The example displays the following output:
// 0 --> False
// 6,121 --> True
// 403,890,774 --> True
// 18,446,744,073,709,551,615 --> True
C#
ulong[] numbers = { UInt64.MinValue, 6121, 403890774, UInt64.MaxValue };
bool result;
foreach (ulong number in numbers)
{
result = Convert.ToBoolean(number);
Console.WriteLine("{0,-26:N0} --> {1}", number, result);
}
// The example displays the following output:
// 0 --> False
// 6,121 --> True
// 403,890,774 --> True
// 18,446,744,073,709,551,615 --> True
let numbers =
[| UInt64.MinValue; 6121uL; 403890774uL; UInt64.MaxValue |]
for number in numbers do
let result = Convert.ToBoolean number
printfn $"{number,-26:N0} --> {result}"
// The example displays the following output:
// 0 --> False
// 6,121 --> True
// 403,890,774 --> True
// 18,446,744,073,709,551,615 --> True
Dim numbers() As ULong = { UInt64.MinValue, 6121, 403890774, UInt64.MaxValue }
Dim result As Boolean
For Each number As ULong In numbers
result = Convert.ToBoolean(number)
Console.WriteLine("{0,-26:N0} --> {1}", number, result)
Next
' The example displays the following output:
' 0 --> False
' 6,121 --> True
' 403,890,774 --> True
' 18,446,744,073,709,551,615 --> True
另请参阅
适用于
.NET 9 和其他版本
| 产品 | 版本 |
|---|---|
| .NET | Core 1.0, Core 1.1, Core 2.0, Core 2.1, Core 2.2, Core 3.0, Core 3.1, 5, 6, 7, 8, 9 |
| .NET Framework | 1.1, 2.0, 3.0, 3.5, 4.0, 4.5, 4.5.1, 4.5.2, 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2, 4.8, 4.8.1 |
| .NET Standard | 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 2.0, 2.1 |
| UWP | 10.0 |
- Source:
- Convert.cs
- Source:
- Convert.cs
- Source:
- Convert.cs
重要
此 API 不符合 CLS。
将指定的 32 位无符号整数的值转换为等效的布尔值。
public:
static bool ToBoolean(System::UInt32 value);C#
[System.CLSCompliant(false)]
public static bool ToBoolean (uint value);[<System.CLSCompliant(false)>]
static member ToBoolean : uint32 -> boolPublic Shared Function ToBoolean (value As UInteger) As Boolean参数
- value
- UInt32
要转换的 32 位无符号整数。
返回
如果 true 不为零，则为 value；否则，为 false。
- 属性
示例
以下示例将值的数组 Int32 转换为 Boolean 值。
array<UInt32>^ numbers = gcnew array<UInt32> { UInt32::MinValue, 612, 4038907, Int32::MaxValue };
bool result;
for each (unsigned int number in numbers)
{
result = Convert::ToBoolean(number);
Console::WriteLine("{0,-15:N0} --> {1}", number, result);
}
// The example displays the following output:
// 0 --> False
// 612 --> True
// 4,038,907 --> True
// 2,147,483,647 --> True
C#
uint[] numbers = { UInt32.MinValue, 612, 4038907, Int32.MaxValue };
bool result;
foreach (uint number in numbers)
{
result = Convert.ToBoolean(number);
Console.WriteLine("{0,-15:N0} --> {1}", number, result);
}
// The example displays the following output:
// 0 --> False
// 612 --> True
// 4,038,907 --> True
// 2,147,483,647 --> True
let numbers =
[| UInt32.MinValue; 612u; 4038907u; uint Int32.MaxValue |]
for number in numbers do
let result = Convert.ToBoolean number
printfn $"{number,-15:N0} --> {result}"
// The example displays the following output:
// 0 --> False
// 612 --> True
// 4,038,907 --> True
// 2,147,483,647 --> True
Dim numbers() As UInteger = { UInt32.MinValue, 612, 4038907, Int32.MaxValue }
Dim result As Boolean
For Each number As UInteger In numbers
result = Convert.ToBoolean(number)
Console.WriteLine("{0,-15:N0} --> {1}", number, result)
Next
' The example displays the following output:
' 0 --> False
' 612 --> True
' 4,038,907 --> True
' 2,147,483,647 --> True
另请参阅
适用于
.NET 9 和其他版本
| 产品 | 版本 |
|---|---|
| .NET | Core 1.0, Core 1.1, Core 2.0, Core 2.1, Core 2.2, Core 3.0, Core 3.1, 5, 6, 7, 8, 9 |
| .NET Framework | 1.1, 2.0, 3.0, 3.5, 4.0, 4.5, 4.5.1, 4.5.2, 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2, 4.8, 4.8.1 |
| .NET Standard | 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 2.0, 2.1 |
| UWP | 10.0 |
- Source:
- Convert.cs
- Source:
- Convert.cs
- Source:
- Convert.cs
重要
此 API 不符合 CLS。
将指定的 16 位无符号整数的值转换为等效的布尔值。
public:
static bool ToBoolean(System::UInt16 value);C#
[System.CLSCompliant(false)]
public static bool ToBoolean (ushort value);[<System.CLSCompliant(false)>]
static member ToBoolean : uint16 -> boolPublic Shared Function ToBoolean (value As UShort) As Boolean参数
- value
- UInt16
要转换的 16 位无符号整数。
返回
如果 true 不为零，则为 value；否则，为 false。
- 属性
示例
以下示例将值的数组 UInt16 转换为 Boolean 值。
array<unsigned short>^ numbers = gcnew array<unsigned short> { UInt16::MinValue, 216, 21453, UInt16::MaxValue };
bool result;
for each (unsigned short number in numbers)
{
result = Convert::ToBoolean(number);
Console::WriteLine("{0,-7:N0} --> {1}", number, result);
}
// The example displays the following output:
// 0 --> False
// 216 --> True
// 21,453 --> True
// 65,535 --> True
C#
ushort[] numbers = { UInt16.MinValue, 216, 21453, UInt16.MaxValue };
bool result;
foreach (ushort number in numbers)
{
result = Convert.ToBoolean(number);
Console.WriteLine("{0,-7:N0} --> {1}", number, result);
}
// The example displays the following output:
// 0 --> False
// 216 --> True
// 21,453 --> True
// 65,535 --> True
let numbers =
[| UInt16.MinValue; 216us; 21453us; UInt16.MaxValue |]
for number in numbers do
let result = Convert.ToBoolean number
printfn $"{number,-7:N0} --> {result}"
// The example displays the following output:
// 0 --> False
// 216 --> True
// 21,453 --> True
// 65,535 --> True
Dim numbers() As UShort = { UInt16.MinValue, 216, 21453, UInt16.MaxValue }
Dim result As Boolean
For Each number As UShort In numbers
result = Convert.ToBoolean(number)
Console.WriteLine("{0,-7:N0} --> {1}", number, result)
Next
' The example displays the following output:
' 0 --> False
' 216 --> True
' 21,453 --> True
' 65,535 --> True
另请参阅
适用于
.NET 9 和其他版本
| 产品 | 版本 |
|---|---|
| .NET | Core 1.0, Core 1.1, Core 2.0, Core 2.1, Core 2.2, Core 3.0, Core 3.1, 5, 6, 7, 8, 9 |
| .NET Framework | 1.1, 2.0, 3.0, 3.5, 4.0, 4.5, 4.5.1, 4.5.2, 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2, 4.8, 4.8.1 |
| .NET Standard | 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 2.0, 2.1 |
| UWP | 10.0 |
- Source:
- Convert.cs
- Source:
- Convert.cs
- Source:
- Convert.cs
将逻辑值的指定字符串表示形式转换为其等效的布尔值。
public:
static bool ToBoolean(System::String ^ value);C#
public static bool ToBoolean (string value);C#
public static bool ToBoolean (string? value);static member ToBoolean : string -> boolPublic Shared Function ToBoolean (value As String) As Boolean参数
- value
- String
包含 TrueString 或 FalseString 值的字符串。
返回
如果 true 等于 value，则为 TrueString；如果 false 等于 value 或 FalseString，则为 null。
例外
value 不等于 TrueString 或 FalseString。
示例
以下示例使用 Convert.ToBoolean(String) 方法将各种字符串转换为布尔值。
using namespace System;
void main()
{
array<String^>^ values = gcnew array<String^> { nullptr, String::Empty,
"true", "TrueString",
"False", " false ",
"-1", "0" };
for each (String^ value in values) {
try
{
Console::WriteLine("Converted '{0}' to {1}.", value,
Convert::ToBoolean(value));
}
catch (FormatException^ e)
{
Console::WriteLine("Unable to convert '{0}' to a Boolean.", value);
}
}
}
// The example displays the following output:
// Converted '' to False.
// Unable to convert '' to a Boolean.
// Converted 'true' to True.
// Unable to convert 'TrueString' to a Boolean.
// Converted 'False' to False.
// Converted ' false ' to False.
// Unable to convert '-1' to a Boolean.
// Unable to convert '0' to a Boolean.
C#
using System;
public class BooleanConversion
{
public static void Main()
{
String[] values = { null, String.Empty, "true", "TrueString",
"False", " false ", "-1", "0" };
foreach (var value in values) {
try
{
Console.WriteLine("Converted '{0}' to {1}.", value,
Convert.ToBoolean(value));
}
catch (FormatException)
{
Console.WriteLine("Unable to convert '{0}' to a Boolean.", value);
}
}
}
}
// The example displays the following output:
// Converted '' to False.
// Unable to convert '' to a Boolean.
// Converted 'true' to True.
// Unable to convert 'TrueString' to a Boolean.
// Converted 'False' to False.
// Converted ' false ' to False.
// Unable to convert '-1' to a Boolean.
// Unable to convert '0' to a Boolean.
open System
let values =
[| null; String.Empty; "true"; "TrueString"
"False"; " false "; "-1"; "0" |]
for value in values do
try
printfn $"Converted '{value}' to {Convert.ToBoolean value}."
with :? FormatException ->
printfn $"Unable to convert '{value}' to a Boolean."
// The example displays the following output:
// Converted '' to False.
// Unable to convert '' to a Boolean.
// Converted 'true' to True.
// Unable to convert 'TrueString' to a Boolean.
// Converted 'False' to False.
// Converted ' false ' to False.
// Unable to convert '-1' to a Boolean.
// Unable to convert '0' to a Boolean.
Module BooleanConversion
Public Sub Main()
Dim values() As String = { Nothing, String.Empty, "true",
"TrueString", "False", " false ",
"-1", "0" }
For Each value In values
Try
Console.WriteLine("Converted '{0}' to {1}.", value, _
Convert.ToBoolean(value))
Catch e As FormatException
Console.WriteLine("Unable to convert '{0}' to a Boolean.", value)
End Try
Next
End Sub
End Module
' The example displays the following output to the console:
' Converted '' to False.
' Unable to convert '' to a Boolean.
' Converted 'true' to True.
' Unable to convert 'TrueString' to a Boolean.
' Converted 'False' to False.
' Converted ' false ' to False.
' Unable to convert '-1' to a Boolean.
' Unable to convert '0' to a Boolean.
注解
若要成功进行转换， value 参数必须等于 Boolean.TrueString，一个值为 True的常量， Boolean.FalseString一个值为 False的常量，或者必须是 null。 与 Boolean.TrueString 和 Boolean.FalseString相比value， 方法忽略大小写以及前导空格和尾随空格。
如果希望在转换失败时不处理异常，可以改为调用 Boolean.TryParse 方法。 它返回一个 Boolean 值，该值指示转换是成功还是失败。
另请参阅
适用于
.NET 9 和其他版本
| 产品 | 版本 |
|---|---|
| .NET | Core 1.0, Core 1.1, Core 2.0, Core 2.1, Core 2.2, Core 3.0, Core 3.1, 5, 6, 7, 8, 9 |
| .NET Framework | 1.1, 2.0, 3.0, 3.5, 4.0, 4.5, 4.5.1, 4.5.2, 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2, 4.8, 4.8.1 |
| .NET Standard | 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 2.0, 2.1 |
| UWP | 10.0 |
- Source:
- Convert.cs
- Source:
- Convert.cs
- Source:
- Convert.cs
将指定的单精度浮点数的值转换为等效的布尔值。
public:
static bool ToBoolean(float value);C#
public static bool ToBoolean (float value);static member ToBoolean : single -> boolPublic Shared Function ToBoolean (value As Single) As Boolean参数
- value
- Single
要转换的单精度浮点数。
返回
如果 true 不为零，则为 value；否则，为 false。
示例
以下示例将值的数组 Single 转换为 Boolean 值。
array<float>^ numbers = gcnew array<float> { Single::MinValue, (float) -193.0012, (float) 20e-15f, 0,
(float) 10551e-10, (float) 100.3398, Single::MaxValue };
bool result;
for each (float number in numbers)
{
result = Convert::ToBoolean(number);
Console::WriteLine("{0,-15} --> {1}", number, result);
}
// The example displays the following output:
// -3.402823E+38 --> True
// -193.0012 --> True
// 2E-14 --> True
// 0 --> False
// 1.0551E-06 --> True
// 100.3398 --> True
// 3.402823E+38 --> True
C#
float[] numbers = { Single.MinValue, -193.0012f, 20e-15f, 0f,
10551e-10f, 100.3398f, Single.MaxValue };
bool result;
foreach (float number in numbers)
{
result = Convert.ToBoolean(number);
Console.WriteLine("{0,-15} --> {1}", number, result);
}
// The example displays the following output:
// -3.402823E+38 --> True
// -193.0012 --> True
// 2E-14 --> True
// 0 --> False
// 1.0551E-06 --> True
// 100.3398 --> True
// 3.402823E+38 --> True
let numbers =
[| Single.MinValue; -193.0012f; 20e-15f; 0f
10551e-10f; 100.3398f; Single.MaxValue |]
for number in numbers do
let result = Convert.ToBoolean number
printfn $"{number,-15} --> {result}"
// The example displays the following output:
// -3.402823E+38 --> True
// -193.0012 --> True
// 2E-14 --> True
// 0 --> False
// 1.0551E-06 --> True
// 100.3398 --> True
// 3.402823E+38 --> True
Dim numbers() As Single = { Single.MinValue, -193.0012, 20e-15, 0, _
10551e-10, 100.3398, Single.MaxValue }
Dim result As Boolean
For Each number As Single In numbers
result = Convert.ToBoolean(number)
Console.WriteLine("{0,-15} --> {1}", number, result)
Next
' The example displays the following output:
' -3.402823E+38 --> True
' -193.0012 --> True
' 2E-14 --> True
' 0 --> False
' 1.0551E-06 --> True
' 100.3398 --> True
' 3.402823E+38 --> True
另请参阅
适用于
.NET 9 和其他版本
| 产品 | 版本 |
|---|---|
| .NET | Core 1.0, Core 1.1, Core 2.0, Core 2.1, Core 2.2, Core 3.0, Core 3.1, 5, 6, 7, 8, 9 |
| .NET Framework | 1.1, 2.0, 3.0, 3.5, 4.0, 4.5, 4.5.1, 4.5.2, 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2, 4.8, 4.8.1 |
| .NET Standard | 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 2.0, 2.1 |
| UWP | 10.0 |
- Source:
- Convert.cs
- Source:
- Convert.cs
- Source:
- Convert.cs
将指定对象的值转换为等效的布尔值。
public:
static bool ToBoolean(System::Object ^ value);C#
public static bool ToBoolean (object value);C#
public static bool ToBoolean (object? value);static member ToBoolean : obj -> boolPublic Shared Function ToBoolean (value As Object) As Boolean参数
- value
- Object
用于实现 IConvertible 接口的对象，或为 null。
返回
true 或 false，它将反映通过对 ToBoolean(IFormatProvider) 的基础类型调用 value 方法而返回的值。 如果 value 为 null，则此方法返回 false。
例外
value 是一个不等于 TrueString 或 FalseString的字符串。
示例
以下示例将对象值的数组转换为 Boolean 值。
array<Object^>^ objects = gcnew array<Object^> { 16.33, -24, 0, "12", "12.7", String::Empty,
"1String", "True", "false", nullptr,
gcnew System::Collections::ArrayList };
for each (Object^ obj in objects)
{
Console::Write("{0,-40} --> ",
obj == nullptr ? "null" :
String::Format("{0} ({1})", obj, obj->GetType()->Name));
try {
Console::WriteLine("{0}", Convert::ToBoolean((Object^) obj));
}
catch (FormatException^) {
Console::WriteLine("Bad Format");
}
catch (InvalidCastException^) {
Console::WriteLine("No Conversion");
}
}
// The example displays the following output:
// 16.33 (Double) --> True
// -24 (Int32) --> True
// 0 (Int32) --> False
// 12 (String) --> Bad Format
// 12.7 (String) --> Bad Format
// (String) --> Bad Format
// 1String (String) --> Bad Format
// True (String) --> True
// false (String) --> False
// null --> False
// System.Collections.ArrayList (ArrayList) --> No Conversion
C#
object[] objects = { 16.33, -24, 0, "12", "12.7", String.Empty,
"1String", "True", "false", null,
new System.Collections.ArrayList() };
foreach (object obj in objects)
{
Console.Write("{0,-40} --> ",
obj != null ?
String.Format("{0} ({1})", obj, obj.GetType().Name) :
"null");
try {
Console.WriteLine("{0}", Convert.ToBoolean(obj));
}
catch (FormatException) {
Console.WriteLine("Bad Format");
}
catch (InvalidCastException) {
Console.WriteLine("No Conversion");
}
}
// The example displays the following output:
// 16.33 (Double) --> True
// -24 (Int32) --> True
// 0 (Int32) --> False
// 12 (String) --> Bad Format
// 12.7 (String) --> Bad Format
// (String) --> Bad Format
// 1String (String) --> Bad Format
// True (String) --> True
// false (String) --> False
// null --> False
// System.Collections.ArrayList (ArrayList) --> No Conversion
let objects: obj[] =
[| 16.33; -24; 0; "12"; "12.7"; String.Empty
"1String"; "True"; "false"; null
System.Collections.ArrayList() |]
for obj in objects do
printf $"""{(if obj <> null then $"{obj} ({obj.GetType().Name})" else "null"),-40} --> """
try
Console.WriteLine("{0}", Convert.ToBoolean(obj))
with
| :? FormatException ->
printfn "Bad Format"
| :? InvalidCastException ->
printfn "No Conversion"
// The example displays the following output:
// 16.33 (Double) --> True
// -24 (Int32) --> True
// 0 (Int32) --> False
// 12 (String) --> Bad Format
// 12.7 (String) --> Bad Format
// (String) --> Bad Format
// 1String (String) --> Bad Format
// True (String) --> True
// false (String) --> False
// null --> False
// System.Collections.ArrayList (ArrayList) --> No Conversion
Dim objects() As Object = {16.33, -24, 0, "12", "12.7", String.Empty, _
"1String", "True", "false", Nothing, _
New System.Collections.ArrayList() }
For Each obj As Object In objects
If obj IsNot Nothing Then
Console.Write("{0,-40} --> ", _
String.Format("{0} ({1})", obj, obj.GetType().Name))
Else
Console.Write("{0,-40} --> ", "Nothing")
End If
Try
Console.WriteLine("{0}", Convert.ToBoolean(obj))
Catch e As FormatException
Console.WriteLine("Bad Format")
Catch e As InvalidCastException
Console.WriteLine("No Conversion")
End Try
Next
' The example displays the following output:
' 16.33 (Double) --> True
' -24 (Int32) --> True
' 0 (Int32) --> False
' 12 (String) --> Bad Format
' 12.7 (String) --> Bad Format
' (String) --> Bad Format
' 1String (String) --> Bad Format
' True (String) --> True
' false (String) --> False
' Nothing --> False
' System.Collections.ArrayList (ArrayList) --> No Conversion
另请参阅
适用于
.NET 9 和其他版本
| 产品 | 版本 |
|---|---|
| .NET | Core 1.0, Core 1.1, Core 2.0, Core 2.1, Core 2.2, Core 3.0, Core 3.1, 5, 6, 7, 8, 9 |
| .NET Framework | 1.1, 2.0, 3.0, 3.5, 4.0, 4.5, 4.5.1, 4.5.2, 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2, 4.8, 4.8.1 |
| .NET Standard | 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 2.0, 2.1 |
| UWP | 10.0 |
- Source:
- Convert.cs
- Source:
- Convert.cs
- Source:
- Convert.cs
调用此方法始终引发 InvalidCastException。
public:
static bool ToBoolean(DateTime value);C#
public static bool ToBoolean (DateTime value);static member ToBoolean : DateTime -> boolPublic Shared Function ToBoolean (value As DateTime) As Boolean参数
- value
- DateTime
要转换的日期和时间值。
返回
不支持此转换。 不返回任何值。
例外
不支持此转换。
示例
以下示例演示尝试将值转换为 DateTime 布尔类型会 InvalidCastException引发 。
public:
void ConvertBoolean()
{
const int year = 1979;
const int month = 7;
const int day = 28;
const int hour = 13;
const int minute = 26;
const int second = 15;
const int millisecond = 53;
DateTime dateTime( year, month, day, hour,
minute, second, millisecond );
bool boolVal;
// System::InvalidCastException is always thrown.
try
{
boolVal = System::Convert::ToBoolean( dateTime );
}
catch ( System::InvalidCastException^ )
{
System::Console::WriteLine( "Conversion from DateTime to Boolean "+
"is not supported by the .NET Framework." );
}
}
C#
public void ConvertBoolean() {
const int year = 1979;
const int month = 7;
const int day = 28;
const int hour = 13;
const int minute = 26;
const int second = 15;
const int millisecond = 53;
DateTime dateTime = new DateTime(year, month, day, hour,
minute, second, millisecond);
bool boolVal;
// System.InvalidCastException is always thrown.
try {
boolVal = System.Convert.ToBoolean(dateTime);
}
catch (System.InvalidCastException) {
System.Console.WriteLine("Conversion from DateTime to " +
"Boolean is not supported by the .NET Framework.");
}
}
let convertBoolean () =
let year = 1979
let month = 7
let day = 28
let hour = 13
let minute = 26
let second = 15
let millisecond = 53
let dateTime = DateTime(year, month, day, hour, minute, second, millisecond)
// System.InvalidCastException is always thrown.
try
let boolVal = Convert.ToBoolean dateTime
()
with :? InvalidCastException ->
printfn "Conversion from DateTime to Boolean is not supported by the .NET Runtime."
Public Sub ConvertBoolean()
Const year As Integer = 1979
Const month As Integer = 7
Const day As Integer = 28
Const hour As Integer = 13
Const minute As Integer = 26
Const second As Integer = 15
Const millisecond As Integer = 53
Dim dateTime As New DateTime(year, month, day, hour, minute, _
second, millisecond)
Dim boolVal As Boolean
' System.InvalidCastException is always thrown.
Try
boolVal = System.Convert.ToBoolean(dateTime)
Catch exception As System.InvalidCastException
System.Console.WriteLine("Conversion from DateTime to " + _
"Boolean is not supported by the .NET Framework.")
End Try
End Sub
适用于
.NET 9 和其他版本
| 产品 | 版本 |
|---|---|
| .NET | Core 2.0, Core 2.1, Core 2.2, Core 3.0, Core 3.1, 5, 6, 7, 8, 9 |
| .NET Framework | 1.1, 2.0, 3.0, 3.5, 4.0, 4.5, 4.5.1, 4.5.2, 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2, 4.8, 4.8.1 |
| .NET Standard | 2.0, 2.1 |
- Source:
- Convert.cs
- Source:
- Convert.cs
- Source:
- Convert.cs
将指定的 32 位有符号整数的值转换为等效的布尔值。
public:
static bool ToBoolean(int value);C#
public static bool ToBoolean (int value);static member ToBoolean : int -> boolPublic Shared Function ToBoolean (value As Integer) As Boolean参数
- value
- Int32
要转换的 32 位带符号整数。
返回
如果 true 不为零，则为 value；否则，为 false。
示例
array<int>^ numbers = gcnew array<int> { Int32::MinValue, -201649, -68, 0, 612, 4038907,
Int32::MaxValue };
bool result;
for each (int number in numbers)
{
result = Convert::ToBoolean(number);
Console::WriteLine("{0,-15:N0} --> {1}", number, result);
}
// The example displays the following output:
// -2,147,483,648 --> True
// -201,649 --> True
// -68 --> True
// 0 --> False
// 612 --> True
// 4,038,907 --> True
// 2,147,483,647 --> True
C#
int[] numbers = { Int32.MinValue, -201649, -68, 0, 612, 4038907,
Int32.MaxValue };
bool result;
foreach (int number in numbers)
{
result = Convert.ToBoolean(number);
Console.WriteLine("{0,-15:N0} --> {1}", number, result);
}
// The example displays the following output:
// -2,147,483,648 --> True
// -201,649 --> True
// -68 --> True
// 0 --> False
// 612 --> True
// 4,038,907 --> True
// 2,147,483,647 --> True
let numbers =
[| Int32.MinValue; -201649; -68; 0
612; 4038907; Int32.MaxValue |]
for number in numbers do
let result = Convert.ToBoolean number
printfn $"{number,-15:N0} --> {result}"
// The example displays the following output:
// -2,147,483,648 --> True
// -201,649 --> True
// -68 --> True
// 0 --> False
// 612 --> True
// 4,038,907 --> True
// 2,147,483,647 --> True
Dim numbers() As Integer = { Int32.MinValue, -201649, -68, 0, 612, _
4038907, Int32.MaxValue }
Dim result As Boolean
For Each number As Integer In numbers
result = Convert.ToBoolean(number)
Console.WriteLine("{0,-15:N0} --> {1}", number, result)
Next
' The example displays the following output:
' -2,147,483,648 --> True
' -201,649 --> True
' -68 --> True
' 0 --> False
' 612 --> True
' 4,038,907 --> True
' 2,147,483,647 --> True
另请参阅
适用于
.NET 9 和其他版本
| 产品 | 版本 |
|---|---|
| .NET | Core 1.0, Core 1.1, Core 2.0, Core 2.1, Core 2.2, Core 3.0, Core 3.1, 5, 6, 7, 8, 9 |
| .NET Framework | 1.1, 2.0, 3.0, 3.5, 4.0, 4.5, 4.5.1, 4.5.2, 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2, 4.8, 4.8.1 |
| .NET Standard | 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 2.0, 2.1 |
| UWP | 10.0 |
- Source:
- Convert.cs
- Source:
- Convert.cs
- Source:
- Convert.cs
将指定的 16 位有符号整数的值转换为等效的布尔值。
public:
static bool ToBoolean(short value);C#
public static bool ToBoolean (short value);static member ToBoolean : int16 -> boolPublic Shared Function ToBoolean (value As Short) As Boolean参数
- value
- Int16
要转换的 16 位带符号整数。
返回
如果 true 不为零，则为 value；否则，为 false。
示例
array<Int16>^ numbers = gcnew array<Int16> { Int16::MinValue, -10000, -154, 0, 216, 21453,
Int16::MaxValue };
bool result;
for each (Int16 number in numbers)
{
result = Convert::ToBoolean(number);
Console::WriteLine("{0,-7:N0} --> {1}", number, result);
}
// The example displays the following output:
// -32,768 --> True
// -10,000 --> True
// -154 --> True
// 0 --> False
// 216 --> True
// 21,453 --> True
// 32,767 --> True
C#
short[] numbers = { Int16.MinValue, -10000, -154, 0, 216, 21453,
Int16.MaxValue };
bool result;
foreach (short number in numbers)
{
result = Convert.ToBoolean(number);
Console.WriteLine("{0,-7:N0} --> {1}", number, result);
}
// The example displays the following output:
// -32,768 --> True
// -10,000 --> True
// -154 --> True
// 0 --> False
// 216 --> True
// 21,453 --> True
// 32,767 --> True
let numbers =
[| Int16.MinValue; -10000s; -154s; 0s
216s; 21453s; Int16.MaxValue |]
for number in numbers do
let result = Convert.ToBoolean number
printfn $"{number,-7:N0} --> {result}"
// The example displays the following output:
// -32,768 --> True
// -10,000 --> True
// -154 --> True
// 0 --> False
// 216 --> True
// 21,453 --> True
// 32,767 --> True
Dim numbers() As Short = { Int16.MinValue, -10000, -154, 0, 216, _
21453, Int16.MaxValue }
Dim result As Boolean
For Each number As Short In numbers
result = Convert.ToBoolean(number)
Console.WriteLine("{0,-7:N0} --> {1}", number, result)
Next
' The example displays the following output:
' -32,768 --> True
' -10,000 --> True
' -154 --> True
' 0 --> False
' 216 --> True
' 21,453 --> True
' 32,767 --> True
另请参阅
适用于
.NET 9 和其他版本
| 产品 | 版本 |
|---|---|
| .NET | Core 1.0, Core 1.1, Core 2.0, Core 2.1, Core 2.2, Core 3.0, Core 3.1, 5, 6, 7, 8, 9 |
| .NET Framework | 1.1, 2.0, 3.0, 3.5, 4.0, 4.5, 4.5.1, 4.5.2, 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2, 4.8, 4.8.1 |
| .NET Standard | 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 2.0, 2.1 |
| UWP | 10.0 |
- Source:
- Convert.cs
- Source:
- Convert.cs
- Source:
- Convert.cs
将指定的双精度浮点数的值转换为等效的布尔值。
public:
static bool ToBoolean(double value);C#
public static bool ToBoolean (double value);static member ToBoolean : double -> boolPublic Shared Function ToBoolean (value As Double) As Boolean参数
- value
- Double
要转换的双精度浮点数。
返回
如果 true 不为零，则为 value；否则，为 false。
示例
以下示例将布尔值转换为 ， Double 将 Double 转换为布尔值。
public:
void ConvertDoubleBool( double doubleVal )
{
bool boolVal;
// Double to bool conversion cannot overflow.
boolVal = System::Convert::ToBoolean( doubleVal );
System::Console::WriteLine( " {0} as a Boolean is: {1}.",
doubleVal, boolVal );
// bool to double conversion cannot overflow.
doubleVal = System::Convert::ToDouble( boolVal );
System::Console::WriteLine( " {0} as a double is: {1}.",
boolVal, doubleVal );
}
C#
public void ConvertDoubleBool(double doubleVal) {
bool boolVal;
// Double to bool conversion cannot overflow.
boolVal = System.Convert.ToBoolean(doubleVal);
System.Console.WriteLine("{0} as a Boolean is: {1}.",
doubleVal, boolVal);
// bool to double conversion cannot overflow.
doubleVal = System.Convert.ToDouble(boolVal);
System.Console.WriteLine("{0} as a double is: {1}.",
boolVal, doubleVal);
}
let convertDoubleBool (doubleVal: float) =
// Double to bool conversion cannot overflow.
let boolVal = Convert.ToBoolean doubleVal
printfn $"{doubleVal} as a Boolean is: {boolVal}."
// bool to double conversion cannot overflow.
let doubleVal = Convert.ToDouble boolVal
printfn $"{boolVal} as a double is: {doubleVal}."
Public Sub ConvertDoubleBool(ByVal doubleVal As Double)
Dim boolVal As Boolean
'Double to Boolean conversion cannot overflow.
boolVal = System.Convert.ToBoolean(doubleVal)
System.Console.WriteLine("{0} as a Boolean is: {1}.", _
doubleVal, boolVal)
'Boolean to Double conversion cannot overflow.
doubleVal = System.Convert.ToDouble(boolVal)
System.Console.WriteLine("{0} as a Double is: {1}.", _
boolVal, doubleVal)
End Sub
另请参阅
适用于
.NET 9 和其他版本
| 产品 | 版本 |
|---|---|
| .NET | Core 1.0, Core 1.1, Core 2.0, Core 2.1, Core 2.2, Core 3.0, Core 3.1, 5, 6, 7, 8, 9 |
| .NET Framework | 1.1, 2.0, 3.0, 3.5, 4.0, 4.5, 4.5.1, 4.5.2, 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2, 4.8, 4.8.1 |
| .NET Standard | 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 2.0, 2.1 |
| UWP | 10.0 |
- Source:
- Convert.cs
- Source:
- Convert.cs
- Source:
- Convert.cs
将指定的十进制数字的值转换为等效的布尔值。
public:
static bool ToBoolean(System::Decimal value);C#
public static bool ToBoolean (decimal value);static member ToBoolean : decimal -> boolPublic Shared Function ToBoolean (value As Decimal) As Boolean参数
- value
- Decimal
要转换的数字。
返回
如果 true 不为零，则为 value；否则，为 false。
示例
以下示例将值数组 Decimal 转换为 Boolean 值。
array<Decimal>^ numbers = gcnew array<Decimal> { Decimal::MinValue, (Decimal) -12034.87,
(Decimal) -100, (Decimal) 0, (Decimal) 300,
(Decimal) 6790823.45, Decimal::MaxValue };
bool result;
for each (Decimal number in numbers)
{
result = Convert::ToBoolean(number);
Console::WriteLine("{0,-30} --> {1}", number, result);
}
// The example displays the following output:
// -79228162514264337593543950335 --> True
// -12034.87 --> True
// -100 --> True
// 0 --> False
// 300 --> True
// 6790823.45 --> True
// 79228162514264337593543950335 --> True
C#
decimal[] numbers = { Decimal.MinValue, -12034.87m, -100m, 0m,
300m, 6790823.45m, Decimal.MaxValue };
bool result;
foreach (decimal number in numbers)
{
result = Convert.ToBoolean(number);
Console.WriteLine("{0,-30} --> {1}", number, result);
}
// The example displays the following output:
// -79228162514264337593543950335 --> True
// -12034.87 --> True
// -100 --> True
// 0 --> False
// 300 --> True
// 6790823.45 --> True
// 79228162514264337593543950335 --> True
let numbers =
[| Decimal.MinValue; -12034.87m; -100m; 0m
300m; 6790823.45m; Decimal.MaxValue |]
for number in numbers do
let result = Convert.ToBoolean number
printfn $"{number,-30} --> {result}"
// The example displays the following output:
// -79228162514264337593543950335 --> True
// -12034.87 --> True
// -100 --> True
// 0 --> False
// 300 --> True
// 6790823.45 --> True
// 79228162514264337593543950335 --> True
Dim numbers() As Decimal = { Decimal.MinValue, -12034.87d, -100d, _
0d, 300d, 6790823.45d, Decimal.MaxValue }
Dim result As Boolean
For Each number As Decimal In numbers
result = Convert.ToBoolean(number)
Console.WriteLine("{0,-30} --> {1}", number, result)
Next
' The example displays the following output:
' -79228162514264337593543950335 --> True
' -12034.87 --> True
' -100 --> True
' 0 --> False
' 300 --> True
' 6790823.45 --> True
' 79228162514264337593543950335 --> True
另请参阅
适用于
.NET 9 和其他版本
| 产品 | 版本 |
|---|---|
| .NET | Core 1.0, Core 1.1, Core 2.0, Core 2.1, Core 2.2, Core 3.0, Core 3.1, 5, 6, 7, 8, 9 |
| .NET Framework | 1.1, 2.0, 3.0, 3.5, 4.0, 4.5, 4.5.1, 4.5.2, 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2, 4.8, 4.8.1 |
| .NET Standard | 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 2.0, 2.1 |
| UWP | 10.0 |
- Source:
- Convert.cs
- Source:
- Convert.cs
- Source:
- Convert.cs
调用此方法始终引发 InvalidCastException。
public:
static bool ToBoolean(char value);C#
public static bool ToBoolean (char value);static member ToBoolean : char -> boolPublic Shared Function ToBoolean (value As Char) As Boolean参数
- value
- Char
要转换的 Unicode 字符。
返回
不支持此转换。 不返回任何值。
例外
不支持此转换。
另请参阅
适用于
.NET 9 和其他版本
| 产品 | 版本 |
|---|---|
| .NET | Core 2.0, Core 2.1, Core 2.2, Core 3.0, Core 3.1, 5, 6, 7, 8, 9 |
| .NET Framework | 1.1, 2.0, 3.0, 3.5, 4.0, 4.5, 4.5.1, 4.5.2, 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2, 4.8, 4.8.1 |
| .NET Standard | 2.0, 2.1 |
- Source:
- Convert.cs
- Source:
- Convert.cs
- Source:
- Convert.cs
将指定的 8 位无符号整数的值转换为等效的布尔值。
public:
static bool ToBoolean(System::Byte value);C#
public static bool ToBoolean (byte value);static member ToBoolean : byte -> boolPublic Shared Function ToBoolean (value As Byte) As Boolean参数
- value
- Byte
要转换的 8 位无符号整数。
返回
如果 true 不为零，则为 value；否则，为 false。
示例
array<Byte>^ bytes = gcnew array<Byte> { Byte::MinValue, 100, 200, Byte::MaxValue };
bool result;
for each (Byte byteValue in bytes)
{
result = Convert::ToBoolean(byteValue);
Console::WriteLine("{0,-5} --> {1}", byteValue, result);
}
// The example displays the following output:
// 0 --> False
// 100 --> True
// 200 --> True
// 255 --> True
C#
byte[] bytes = { Byte.MinValue, 100, 200, Byte.MaxValue };
bool result;
foreach (byte byteValue in bytes)
{
result = Convert.ToBoolean(byteValue);
Console.WriteLine("{0,-5} --> {1}", byteValue, result);
}
// The example displays the following output:
// 0 --> False
// 100 --> True
// 200 --> True
// 255 --> True
let bytes = [| Byte.MinValue; 100uy; 200uy; Byte.MaxValue |]
for byteValue in bytes do
let result = Convert.ToBoolean byteValue
printfn $"{byteValue,-5} --> {result}"
// The example displays the following output:
// 0 --> False
// 100 --> True
// 200 --> True
// 255 --> True
Dim bytes() As Byte = { Byte.MinValue, 100, 200, Byte.MaxValue }
Dim result As Boolean
For Each byteValue As Byte In bytes
result = Convert.ToBoolean(byteValue)
Console.WriteLine("{0,-5} --> {1}", byteValue, result)
Next
' The example displays the following output:
' 0 --> False
' 100 --> True
' 200 --> True
' 255 --> True
另请参阅
适用于
.NET 9 和其他版本
| 产品 | 版本 |
|---|---|
| .NET | Core 1.0, Core 1.1, Core 2.0, Core 2.1, Core 2.2, Core 3.0, Core 3.1, 5, 6, 7, 8, 9 |
| .NET Framework | 1.1, 2.0, 3.0, 3.5, 4.0, 4.5, 4.5.1, 4.5.2, 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2, 4.8, 4.8.1 |
| .NET Standard | 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 2.0, 2.1 |
| UWP | 10.0 |
- Source:
- Convert.cs
- Source:
- Convert.cs
- Source:
- Convert.cs
返回指定的布尔值；不执行任何实际的转换。
public:
static bool ToBoolean(bool value);C#
public static bool ToBoolean (bool value);static member ToBoolean : bool -> boolPublic Shared Function ToBoolean (value As Boolean) As Boolean参数
- value
- Boolean
要返回的布尔值。
返回
不经更改即返回 value。
另请参阅
适用于
.NET 9 和其他版本
| 产品 | 版本 |
|---|---|
| .NET | Core 1.0, Core 1.1, Core 2.0, Core 2.1, Core 2.2, Core 3.0, Core 3.1, 5, 6, 7, 8, 9 |
| .NET Framework | 1.1, 2.0, 3.0, 3.5, 4.0, 4.5, 4.5.1, 4.5.2, 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2, 4.8, 4.8.1 |
| .NET Standard | 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 2.0, 2.1 |
| UWP | 10.0 |
- Source:
- Convert.cs
- Source:
- Convert.cs
- Source:
- Convert.cs
将指定的 64 位有符号整数的值转换为等效的布尔值。
public:
static bool ToBoolean(long value);C#
public static bool ToBoolean (long value);static member ToBoolean : int64 -> boolPublic Shared Function ToBoolean (value As Long) As Boolean参数
- value
- Int64
要转换的 64 位带符号整数。
返回
如果 true 不为零，则为 value；否则，为 false。
示例
array<Int64>^ numbers = gcnew array<Int64> { Int64::MinValue, -2016493, -689, 0, 6121,
403890774, Int64::MaxValue };
bool result;
for each (Int64 number in numbers)
{
result = Convert::ToBoolean(number);
Console::WriteLine("{0,-26:N0} --> {1}", number, result);
}
// The example displays the following output:
// -9,223,372,036,854,775,808 --> True
// -2,016,493 --> True
// -689 --> True
// 0 --> False
// 6,121 --> True
// 403,890,774 --> True
// 9,223,372,036,854,775,807 --> True
C#
long[] numbers = { Int64.MinValue, -2016493, -689, 0, 6121,
403890774, Int64.MaxValue };
bool result;
foreach (long number in numbers)
{
result = Convert.ToBoolean(number);
Console.WriteLine("{0,-26:N0} --> {1}", number, result);
}
// The example displays the following output:
// -9,223,372,036,854,775,808 --> True
// -2,016,493 --> True
// -689 --> True
// 0 --> False
// 6,121 --> True
// 403,890,774 --> True
// 9,223,372,036,854,775,807 --> True
let numbers =
[| Int64.MinValue; -2016493; -689
0; 6121; 403890774; Int64.MaxValue |]
for number in numbers do
let result = Convert.ToBoolean number
printfn $"{number,-26:N0} --> {result}"
// The example displays the following output:
// -9,223,372,036,854,775,808 --> True
// -2,016,493 --> True
// -689 --> True
// 0 --> False
// 6,121 --> True
// 403,890,774 --> True
// 9,223,372,036,854,775,807 --> True
Dim numbers() As Long = { Int64.MinValue, -2016493, -689, 0, 6121, _
403890774, Int64.MaxValue }
Dim result As Boolean
For Each number As Long In numbers
result = Convert.ToBoolean(number)
Console.WriteLine("{0,-26:N0} --> {1}", number, result)
Next
' The example displays the following output:
' -9,223,372,036,854,775,808 --> True
' -2,016,493 --> True
' -689 --> True
' 0 --> False
' 6,121 --> True
' 403,890,774 --> True
' 9,223,372,036,854,775,807 --> True
另请参阅
适用于
.NET 9 和其他版本
| 产品 | 版本 |
|---|---|
| .NET | Core 1.0, Core 1.1, Core 2.0, Core 2.1, Core 2.2, Core 3.0, Core 3.1, 5, 6, 7, 8, 9 |
| .NET Framework | 1.1, 2.0, 3.0, 3.5, 4.0, 4.5, 4.5.1, 4.5.2, 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2, 4.8, 4.8.1 |
| .NET Standard | 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 2.0, 2.1 |
| UWP | 10.0 |
